powerpc/mpc83xx: cleanup makefile for mpc83xx

Remove symbolic link generated by compiling. Fix makefile for out-of-tree
compiling error.

Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
diff --git a/Makefile b/Makefile
index 294c762..5017f3b 100644
--- a/Makefile
+++ b/Makefile
@@ -793,6 +793,7 @@
 	@rm -f $(obj)u-boot.dtb
 	@rm -f $(obj)tools/{env/crc32.c,inca-swap-bytes}
 	@rm -f $(obj)arch/powerpc/cpu/mpc824x/bedbug_603e.c
+	@rm -f $(obj)arch/powerpc/cpu/mpc83xx/ddr-gen?.c
 	@rm -fr $(obj)include/asm/proc $(obj)include/asm/arch $(obj)include/asm
 	@rm -fr $(obj)include/generated
 	@[ ! -d $(obj)nand_spl ] || find $(obj)nand_spl -name "*" -type l -print | xargs rm -f