MIPS: BMIPS: Drop unnecessary assembler flag

Nowadays GCC will always pass -march flag to gas, so there
is no need to pass another mips32 flag to assembler.
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/Makefile

@@ -170,7 +170,7 @@ cflags-$(CONFIG_CPU_NEVADA)	+= $(call cc-option,-march=rm5200,-march=mips4) \
 			-Wa,--trap
 cflags-$(CONFIG_CPU_RM7000)	+= $(call cc-option,-march=rm7000,-march=mips4) \
 			-Wa,--trap
-cflags-$(CONFIG_CPU_SB1)	+= $(call cc-option,-march=sb1,-march=mips64) \
+cflags-$(CONFIG_CPU_SB1)	+= $(call cc-option,-march=sb1,-march=mips64r1) \
 			-Wa,--trap
 cflags-$(CONFIG_CPU_SB1)	+= $(call cc-option,-mno-mdmx)
 cflags-$(CONFIG_CPU_SB1)	+= $(call cc-option,-mno-mips3d)
@@ -178,7 +178,7 @@ cflags-$(CONFIG_CPU_R10000)	+= $(call cc-option,-march=r10000,-march=mips4) \
 			-Wa,--trap
 cflags-$(CONFIG_CPU_CAVIUM_OCTEON) += -march=octeon -Wa,--trap
 cflags-$(CONFIG_CAVIUM_CN63XXP1) += -Wa,-mfix-cn63xxp1
-cflags-$(CONFIG_CPU_BMIPS)	+= -march=mips32 -Wa,-mips32 -Wa,--trap
+cflags-$(CONFIG_CPU_BMIPS)	+= -march=mips32 -Wa,--trap
 
 cflags-$(CONFIG_CPU_LOONGSON2E) += \
 			$(call cc-option,-march=loongson2e,-march=mips3) -Wa,--trap