kbuild: allow assignment to {A,C}FLAGS_KERNEL on the command line

It is now possible to assign options to AS and CC
on the command line - which is only used for built-in code.

{A,C}FLAGS_KERNEL was used both in the top-level Makefile
in the arch makefiles, thus users had no way to specify
additional options to AS, CC without overriding
the original value.

Introduce a new set of variables KBUILD_{A,C}FLAGS_KERNEL
that is used by arch specific files and free up
{A,C}FLAGS_KERNEL so they can be assigned on
the command line.

All arch Makefiles that used the old variables has been updated.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/arch/ia64/Makefile b/arch/ia64/Makefile
index 5ab6af3..62b10f5 100644
--- a/arch/ia64/Makefile
+++ b/arch/ia64/Makefile
@@ -23,12 +23,12 @@
 OBJCOPYFLAGS	:= --strip-all
 LDFLAGS_vmlinux	:= -static
 KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/ia64/module.lds
-AFLAGS_KERNEL	:= -mconstant-gp
+KBUILD_AFLAGS_KERNEL := -mconstant-gp
 EXTRA		:=
 
 cflags-y	:= -pipe $(EXTRA) -ffixed-r13 -mfixed-range=f12-f15,f32-f127 \
 		   -falign-functions=32 -frename-registers -fno-optimize-sibling-calls
-CFLAGS_KERNEL	:= -mconstant-gp
+KBUILD_CFLAGS_KERNEL := -mconstant-gp
 
 GAS_STATUS	= $(shell $(srctree)/arch/ia64/scripts/check-gas "$(CC)" "$(OBJDUMP)")
 KBUILD_CPPFLAGS += $(shell $(srctree)/arch/ia64/scripts/toolchain-flags "$(CC)" "$(OBJDUMP)" "$(READELF)")