ARM: refactor compiler options in config.mk

Every ARM cpu config.mk (arch/arm/cpu/{CPUDIR}/config.mk) defines:

PLATFORM_RELFLAGS += -fno-common -ffixed-r8 -msoft-float

So, this patch moves the common compiler options to arch/arm/config.mk.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/arch/arm/config.mk b/arch/arm/config.mk
index 19451ba..16c2e3d 100644
--- a/arch/arm/config.mk
+++ b/arch/arm/config.mk
@@ -16,7 +16,8 @@
 endif
 
 LDFLAGS_FINAL += --gc-sections
-PLATFORM_RELFLAGS += -ffunction-sections -fdata-sections
+PLATFORM_RELFLAGS += -ffunction-sections -fdata-sections \
+                     -fno-common -ffixed-r8 -msoft-float
 
 # Support generic board on ARM
 __HAVE_ARCH_GENERIC_BOARD := y