sh: Wrap CPU tuning through cc-option.

Some compilers don't support the explicit CPU tuning, while binutils
is still able to handle the special subtype-specific opcodes. Make
the CFLAG optional, falling back on the compiler default if nothing
better exists.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/Makefile

@@ -34,12 +34,14 @@ isa-y			:= $(isa-y)-nofpu
 endif
 endif
 
-cflags-$(CONFIG_CPU_SH2)		:= -m2
-cflags-$(CONFIG_CPU_SH2A)		:= -m2a $(call cc-option,-m2a-nofpu,)
-cflags-$(CONFIG_CPU_SH3)		:= -m3
-cflags-$(CONFIG_CPU_SH4)		:= -m4 \
+cflags-$(CONFIG_CPU_SH2)		:= $(call cc-option,-m2,)
+cflags-$(CONFIG_CPU_SH2A)		:= $(call cc-option,-m2a,) \
+					   $(call cc-option,-m2a-nofpu,)
+cflags-$(CONFIG_CPU_SH3)		:= $(call cc-option,-m3,)
+cflags-$(CONFIG_CPU_SH4)		:= $(call cc-option,-m4,) \
 	$(call cc-option,-mno-implicit-fp,-m4-nofpu)
-cflags-$(CONFIG_CPU_SH4A)		:= $(call cc-option,-m4a,) $(call cc-option,-m4a-nofpu,)
+cflags-$(CONFIG_CPU_SH4A)		:= $(call cc-option,-m4a,) \
+					   $(call cc-option,-m4a-nofpu,)
 
 cflags-$(CONFIG_CPU_BIG_ENDIAN)		+= -mb
 cflags-$(CONFIG_CPU_LITTLE_ENDIAN)	+= -ml