sh: merge compiler flag -ffixed-r13

-ffixed-r13 is defined commonly for sh2, sh3, sh4.
Move it to arch/sh/config.mk

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>

arch/sh/config.mk

@@ -15,3 +15,4 @@ endif
 PLATFORM_CPPFLAGS += -DCONFIG_SH -D__SH__
 PLATFORM_LDFLAGS += -e $(CONFIG_SYS_TEXT_BASE) --defsym reloc_dst=$(CONFIG_SYS_TEXT_BASE)
 LDFLAGS_FINAL = --gc-sections
+PLATFORM_RELFLAGS += -ffixed-r13

arch/sh/cpu/sh2/config.mk

@@ -14,5 +14,4 @@ PLATFORM_CPPFLAGS += -m3e -mb
 endif
 PLATFORM_CPPFLAGS += -DCONFIG_SH2 $(call cc-option,-mno-fdpic)
 
-PLATFORM_RELFLAGS += -ffixed-r13
 PLATFORM_LDFLAGS += $(ENDIANNESS)

arch/sh/cpu/sh3/config.mk

@@ -12,4 +12,3 @@
 #
 #
 PLATFORM_CPPFLAGS += -DCONFIG_SH3 -m3
-PLATFORM_RELFLAGS += -ffixed-r13

arch/sh/cpu/sh4/config.mk

@@ -9,4 +9,3 @@
 #
 #
 PLATFORM_CPPFLAGS += -DCONFIG_SH4 -m4-nofpu
-PLATFORM_RELFLAGS += -ffixed-r13