ppc64: use sstep.c from powerpc/lib

since it is identical to sstep.c from ppc64/lib.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

arch/powerpc/lib/Makefile

@@ -5,7 +5,7 @@
 ifeq ($(CONFIG_PPC_MERGE),y)
 obj-y			:= strcase.o string.o
 obj-$(CONFIG_PPC32)	+= div64.o copy_32.o checksum_32.o
-obj-$(CONFIG_PPC64)	+= usercopy_64.o sstep.o mem_64.o
+obj-$(CONFIG_PPC64)	+= usercopy_64.o mem_64.o
 endif
 
 obj-$(CONFIG_PPC64)	+= checksum_64.o copypage_64.o copyuser_64.o \
@@ -13,4 +13,5 @@ obj-$(CONFIG_PPC64)	+= checksum_64.o copypage_64.o copyuser_64.o \
 obj-$(CONFIG_PPC_ISERIES) += e2a.o
 ifeq ($(CONFIG_PPC64),y)
 obj-$(CONFIG_SMP)	+= locks.o
+obj-$(CONFIG_DEBUG_KERNEL) += sstep.o
 endif