kirkwood: support CONFIG_SYS_THUMB_BUILD

Kirkwood files cpu.c and cache.c cannot build in Thumb state;
force them in ARM state even under CONFIG_SYS_THUMB_BUILD.

Signed-off-by: Albert ARIBAUD <albert.u.boot@aribaud.net>

arch/arm/mach-kirkwood/Makefile

@@ -9,3 +9,9 @@
 obj-y	= cpu.o
 obj-y	+= cache.o
 obj-y	+= mpp.o
+
+# cpu.o and cache.o contain CP15 instructions which cannot be run in
+# Thumb state, so build them for ARM state even with CONFIG_SYS_THUMB_BUILD
+
+CFLAGS_cpu.o := -marm
+CFLAGS_cache.o := -marm