MIPS: Kconfig: optimize gcc -march and -mtune setup

Move setup of -march to arch/mips/Makefile and follow the design on ARM.
Also add a possibility to chose specific CPU tune options.

Signed-off-by: Wills Wang <wills.wang@live.com>
Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index 6a9f798..90cd590 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -13,3 +13,16 @@
 libs-y += $(machdirs)
 
 PLATFORM_CPPFLAGS += $(patsubst %,-I$(srctree)/%include,$(machdirs))
+
+# Optimize for MIPS architectures
+arch-$(CONFIG_CPU_MIPS32_R1) += -march=mips32 -Wa,-mips32
+arch-$(CONFIG_CPU_MIPS32_R2) += -march=mips32r2 -Wa,-mips32r2
+arch-$(CONFIG_CPU_MIPS64_R1) += -march=mips64 -Wa,-mips64
+arch-$(CONFIG_CPU_MIPS64_R2) += -march=mips64r2 -Wa,-mips64r2
+
+# Allow extra optimization for specific CPUs/SoCs
+tune-$(CONFIG_MIPS_TUNE_4KC) += -mtune=4kc
+tune-$(CONFIG_MIPS_TUNE_14KC) += -mtune=14kc
+tune-$(CONFIG_MIPS_TUNE_24KC) += -mtune=24kc
+
+PLATFORM_CPPFLAGS += $(arch-y) $(tune-y)