kbuild: move asm-offsets.c from SoC directory to arch/$(ARCH)/lib

U-Boot has supported two kinds of asm-offsets.h.

One is generic for all architectures and its source is located at
./lib/asm-offsets.c.

The other is SoC specific and its source is under SoC directory.
The problem here is that only boards with SoC directory can use
the asm-offsets infrastructure.
Putting asm-offsets.c right under CPU directory does not work.

Now a new demand is coming. PowerPC folks want to use asm-offsets.
But no PowerPC boards have SoC directory.

It seems inconsistent that some boards add asm-offsets.c to SoC
directoreis and some to CPU directories.
It looks more reasonable to put asm-offsets.c under arch/$(ARCH)/lib.

This commit merges asm-offsets.c under SoC directories into
arch/$(ARCH)/lib/asm-offsets.c.

By the way, I doubt the necessity of some entries in asm-offsets.c.
I am leaving refactoring to the board maintainers.
Please check "TODO" in the comment blocks in
arch/{arm,nds32}/lib/asm-offsets.c.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Yuantian Tang <Yuantian.Tang@freescale.com>

Kbuild

@@ -42,13 +42,13 @@ $(obj)/$(generic-offsets-file): lib/asm-offsets.s Kbuild
 # 2) Generate asm-offsets.h
 #
 
-ifneq ($(wildcard $(srctree)/$(CPUDIR)/$(SOC)/asm-offsets.c),)
+ifneq ($(wildcard $(srctree)/arch/$(ARCH)/lib/asm-offsets.c),)
 offsets-file := include/generated/asm-offsets.h
 endif
 
 always  += $(offsets-file)
 targets += $(offsets-file)
-targets += $(CPUDIR)/$(SOC)/asm-offsets.s
+targets += arch/$(ARCH)/lib/asm-offsets.s
 
 
 # Default sed regexp - multiline due to syntax constraints
@@ -79,9 +79,9 @@ define cmd_offsets
 endef
 
 # We use internal kbuild rules to avoid the "is up to date" message from make
-$(CPUDIR)/$(SOC)/asm-offsets.s: $(CPUDIR)/$(SOC)/asm-offsets.c FORCE
+arch/$(ARCH)/lib/asm-offsets.s: arch/$(ARCH)/lib/asm-offsets.c FORCE
 	$(Q)mkdir -p $(dir $@)
 	$(call if_changed_dep,cc_s_c)
 
-$(obj)/$(offsets-file): $(CPUDIR)/$(SOC)/asm-offsets.s
+$(obj)/$(offsets-file): arch/$(ARCH)/lib/asm-offsets.s Kbuild
 	$(call cmd,offsets)