kbuild: rename prepare to archprepare to fix dependency chain

When introducing the generic asm-offsets.h support the dependency
chain for the prepare targets was changed. All build scripts expecting
include/asm/asm-offsets.h to be made when using the prepare target would broke.
With the limited number of prepare targets left in arch Makefiles
the trivial solution was to introduce a new arch specific target: archprepare

The dependency chain looks like this now:

prepare
  |
  +--> prepare0
         |
         +--> archprepare
                |
		+--> scripts_basic
                +--> prepare1
                       |
                       +---> prepare2
                               |
                               +--> prepare3

So prepare 3 is processed before prepare2 etc.
This guaantees that the asm symlink, version.h, scripts_basic
are all updated before archprepare is processed.

prepare0 which build the asm-offsets.h file will need the
actions performed by archprepare.

The head target is now named prepare, because users scripts will most
likely use that target, but prepare-all has been kept for compatibility.
Updated Documentation/kbuild/makefiles.txt.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index e625ac6..130e622 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -175,7 +175,7 @@
 endif
 	@touch $@
 
-prepare: maketools include/asm-arm/.arch
+archprepare: maketools include/asm-arm/.arch
 
 .PHONY: maketools FORCE
 maketools: include/linux/version.h FORCE
diff --git a/arch/cris/Makefile b/arch/cris/Makefile
index a00043a..ea65d58 100644
--- a/arch/cris/Makefile
+++ b/arch/cris/Makefile
@@ -107,7 +107,7 @@
 	rm -f timage vmlinux.bin decompress.bin rescue.bin cramfs.img
 	rm -rf $(LD_SCRIPT).tmp
 
-prepare: $(SRC_ARCH)/.links $(srctree)/include/asm-$(ARCH)/.arch
+archprepare: $(SRC_ARCH)/.links $(srctree)/include/asm-$(ARCH)/.arch
 
 # Create some links to make all tools happy
 $(SRC_ARCH)/.links:
diff --git a/arch/ia64/Makefile b/arch/ia64/Makefile
index 7ed678c..70f8ed2 100644
--- a/arch/ia64/Makefile
+++ b/arch/ia64/Makefile
@@ -82,7 +82,7 @@
 archclean:
 	$(Q)$(MAKE) $(clean)=$(boot)
 
-prepare:  include/asm-ia64/.offsets.h.stamp
+archprepare:  include/asm-ia64/.offsets.h.stamp
 
 include/asm-ia64/.offsets.h.stamp:
 	mkdir -p include/asm-ia64
diff --git a/arch/ppc/Makefile b/arch/ppc/Makefile
index 6dd7b50..16e2675 100644
--- a/arch/ppc/Makefile
+++ b/arch/ppc/Makefile
@@ -107,7 +107,7 @@
 	# Temporary hack until we have migrated to asm-powerpc
 	$(Q)rm -rf arch/$(ARCH)/include
 
-prepare: checkbin
+archprepare: checkbin
 
 # Temporary hack until we have migrated to asm-powerpc
 include/asm: arch/$(ARCH)/include/asm
diff --git a/arch/sh/Makefile b/arch/sh/Makefile
index 19f00d5..4a30490 100644
--- a/arch/sh/Makefile
+++ b/arch/sh/Makefile
@@ -152,7 +152,7 @@
 	@touch $@
 
 
-prepare: maketools include/asm-sh/.cpu include/asm-sh/.mach
+archprepare: maketools include/asm-sh/.cpu include/asm-sh/.mach
 
 .PHONY: maketools FORCE
 maketools:  include/linux/version.h FORCE
diff --git a/arch/sh64/Makefile b/arch/sh64/Makefile
index 3907373..8ca57ff 100644
--- a/arch/sh64/Makefile
+++ b/arch/sh64/Makefile
@@ -73,7 +73,7 @@
 archclean:
 	$(Q)$(MAKE) $(clean)=$(boot)
 
-prepare: arch/$(ARCH)/lib/syscalltab.h
+archprepare: arch/$(ARCH)/lib/syscalltab.h
 
 define filechk_gen-syscalltab
        (set -e; \
diff --git a/arch/um/Makefile b/arch/um/Makefile
index 154803a..ce98726 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -107,7 +107,7 @@
 $(shell cd $(ARCH_DIR) && ln -sf Kconfig.$(SUBARCH) Kconfig.arch)
 endif
 
-prepare: $(ARCH_SYMLINKS) $(SYS_HEADERS) $(GEN_HEADERS)
+archprepare: $(ARCH_SYMLINKS) $(SYS_HEADERS) $(GEN_HEADERS)
 
 LINK-$(CONFIG_LD_SCRIPT_STATIC) += -static
 LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib
diff --git a/arch/xtensa/Makefile b/arch/xtensa/Makefile
index 67ef4cd..98fac848 100644
--- a/arch/xtensa/Makefile
+++ b/arch/xtensa/Makefile
@@ -66,7 +66,7 @@
 
 archinc		:= include/asm-xtensa
 
-prepare: $(archinc)/.platform
+archprepare: $(archinc)/.platform
 
 # Update machine cpu and platform symlinks if something which affects
 # them changed.