microblaze: Use correct kbuild variable KBUILD_CFLAGS

Fixes the bug introduced in 9552158573f847aa429334bb97995bb290bb4b0d

Signed-off-by: John Williams <john.williams@petalogix.com>

arch/microblaze/Makefile

@@ -37,12 +37,12 @@ CPUFLAGS-$(CONFIG_XILINX_MICROBLAZE0_USE_PCMP_INSTR) += -mxl-pattern-compare
 CPUFLAGS-1 += $(call cc-option,-mcpu=v$(CPU_VER))
 
 # r31 holds current when in kernel mode
-KBUILD_KERNEL += -ffixed-r31 $(CPUFLAGS-1) $(CPUFLAGS-2)
+KBUILD_CFLAGS += -ffixed-r31 $(CPUFLAGS-1) $(CPUFLAGS-2)
 
 LDFLAGS		:=
 LDFLAGS_vmlinux	:=
 
-LIBGCC := $(shell $(CC) $(KBUILD_KERNEL) -print-libgcc-file-name)
+LIBGCC := $(shell $(CC) $(KBUILD_CFLAGS) -print-libgcc-file-name)
 
 head-y := arch/microblaze/kernel/head.o
 libs-y += arch/microblaze/lib/