powerpc/boot: add simpleImage.* to clean-files list

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

arch/powerpc/boot/Makefile

@@ -367,7 +367,7 @@ install: $(CONFIGURE) $(addprefix $(obj)/, $(image-y))
 clean-files += $(image-) $(initrd-) cuImage.* dtbImage.* treeImage.* \
 	zImage zImage.initrd zImage.chrp zImage.coff zImage.holly \
 	zImage.iseries zImage.miboot zImage.pmac zImage.pseries \
-	otheros.bld *.dtb
+	simpleImage.* otheros.bld *.dtb
 
 # clean up files cached by wrapper
 clean-kernel := vmlinux.strip vmlinux.bin