Build arch/$ARCH/lib/bootm.o depending on CONFIG_CMD_BOOTM

MAKEALL is fine for ppc4xx and mpc85xx.
Run checks were done on our controlcenterd hardware.

Signed-off-by: Dirk Eibach <dirk.eibach@gdsys.cc>
Signed-off-by: Andy Fleming <afleming@freescale.com>
diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index 59c723b..8c4920b 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -63,7 +63,7 @@
 COBJS-y	+= board.o
 endif
 endif
-COBJS-y	+= bootm.o
+COBJS-$(CONFIG_CMD_BOOTM) += bootm.o
 COBJS-y	+= cache.o
 COBJS-y	+= extable.o
 COBJS-y	+= interrupts.o