ppc64: Include arch/powerpc/kernel/setup-common.o

... which is needed now that ARCH=ppc64 is using the merged
setup_64.c.
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/Makefile

@@ -46,7 +46,8 @@ endif
 
 else
 # stuff used from here for ARCH=ppc or ARCH=ppc64
-obj-$(CONFIG_PPC64)		+= traps.o process.o init_task.o time.o
+obj-$(CONFIG_PPC64)		+= traps.o process.o init_task.o time.o \
+				   setup-common.o
 
 
 endif