ppc: Move conditional compilation of kgdb.c to Makefile

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/lib_ppc/Makefile b/lib_ppc/Makefile
index 399b41e..60a7625 100644
--- a/lib_ppc/Makefile
+++ b/lib_ppc/Makefile
@@ -35,7 +35,7 @@
 COBJS-y	+= cache.o
 COBJS-y	+= extable.o
 COBJS-y	+= interrupts.o
-COBJS-y	+= kgdb.o
+COBJS-$(CONFIG_CMD_KGDB) += kgdb.o
 COBJS-y	+= time.o
 
 SRCS	:= $(SOBJS-y:.o=.S) $(COBJS-y:.o=.c)