mips: Add MIPS 74Kc tune

Add MIPS 74Kc tune Kconfig option.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Cc: Wills Wang <wills.wang@live.com>
[added missing tune-y entry in arch/mips/Makefile]
Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>

arch/mips/Kconfig

@@ -198,6 +198,9 @@ config MIPS_TUNE_14KC
 config MIPS_TUNE_24KC
 	bool
 
+config MIPS_TUNE_74KC
+	bool
+
 config 32BIT
 	bool
 

arch/mips/Makefile

@@ -26,6 +26,7 @@ arch-$(CONFIG_CPU_MIPS64_R2) += -march=mips64r2 -Wa,-mips64r2
 tune-$(CONFIG_MIPS_TUNE_4KC) += -mtune=4kc
 tune-$(CONFIG_MIPS_TUNE_14KC) += -mtune=14kc
 tune-$(CONFIG_MIPS_TUNE_24KC) += -mtune=24kc
+tune-$(CONFIG_MIPS_TUNE_74KC) += -mtune=74kc
 
 # Include default header files
 cflags-y += -I$(srctree)/arch/mips/include/asm/mach-generic