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

It is now possible to assign options to AS, CC and LD
on the command line - which is only used when building modules.

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

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

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

Note: Previously we had a MODFLAGS variable for both
AS and CC. But in favour of consistency this was dropped.
So in some cases arch Makefile has one assignmnet replaced by
two assignmnets.

Note2: MODFLAGS was not documented and is dropped
without any notice. I do not expect much/any breakage
from this.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Chen Liqin <liqin.chen@sunplusct.com>
Acked-by: Mike Frysinger <vapier@gentoo.org> [blackfin]
Acked-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com> [avr32]
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/Makefile.modpost

@@ -107,7 +107,7 @@ $(modules:.ko=.mod.c): __modpost ;
 modname = $(notdir $(@:.mod.o=))
 
 quiet_cmd_cc_o_c = CC      $@
-      cmd_cc_o_c = $(CC) $(c_flags) $(CFLAGS_MODULE)	\
+      cmd_cc_o_c = $(CC) $(c_flags) $(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE) \
 		   -c -o $@ $<
 
 $(modules:.ko=.mod.o): %.mod.o: %.mod.c FORCE
@@ -117,8 +117,9 @@ targets += $(modules:.ko=.mod.o)
 
 # Step 6), final link of the modules
 quiet_cmd_ld_ko_o = LD [M]  $@
-      cmd_ld_ko_o = $(LD) -r $(LDFLAGS) $(LDFLAGS_MODULE) -o $@		\
-			  $(filter-out FORCE,$^)
+      cmd_ld_ko_o = $(LD) -r $(LDFLAGS)                                 \
+                             $(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE) \
+                             -o $@ $(filter-out FORCE,$^)
 
 $(modules): %.ko :%.o %.mod.o FORCE
 	$(call if_changed,ld_ko_o)