kbuild: mips use generic asm-offsets.h support

Removed obsolete stuff from arch makefile.
mips had a special rule for generating asm-offsets.h so preserved it
using an architecture specific hook in top-level Kbuild file.
Renamed .h file to asm-offsets.h

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index b0fdaee..346e803 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -720,38 +720,7 @@
 	@$(MAKE) $(clean)=arch/mips/boot
 	@$(MAKE) $(clean)=arch/mips/lasat
 
-# Generate <asm/offset.h
-#
-# The default rule is suffering from funny problems on MIPS so we using our
-# own ...
-#
-# ---------------------------------------------------------------------------
 
-define filechk_gen-asm-offset.h
-	(set -e; \
-	 echo "#ifndef _ASM_OFFSET_H"; \
-	 echo "#define _ASM_OFFSET_H"; \
-	 echo "/*"; \
-	 echo " * DO NOT MODIFY."; \
-	 echo " *"; \
-	 echo " * This file was generated by arch/$(ARCH)/Makefile"; \
-	 echo " *"; \
-	 echo " */"; \
-	 echo ""; \
-	 sed -ne "/^@@@/s///p"; \
-	 echo "#endif /* _ASM_OFFSET_H */" )
-endef
-
-prepare: include/asm-$(ARCH)/offset.h
-
-arch/$(ARCH)/kernel/offset.s: include/asm include/linux/version.h \
-				   include/config/MARKER
-
-include/asm-$(ARCH)/offset.h: arch/$(ARCH)/kernel/offset.s
-	$(call filechk,gen-asm-offset.h)
-
-CLEAN_FILES += include/asm-$(ARCH)/offset.h.tmp \
-	       include/asm-$(ARCH)/offset.h \
-	       vmlinux.32 \
+CLEAN_FILES += vmlinux.32 \
 	       vmlinux.64 \
 	       vmlinux.ecoff