[POWERPC] Fix make rules for treeImage.initrd

At present attempting to build treeImage.initrd.* boot images will
fail, because make will select the treeImage.% rule which also matches
instead of the correct and more specific treeImage.initrd.% rule.
This patch corrects the problem by listing the more specific rule
first.

Signed-off-by: David Gibson <[e-mail]>
Signed-off-by: Paul Mackerras <[e-mail]>

arch/powerpc/boot/Makefile

···
 $(obj)/cuImage.%: vmlinux $(dts) $(wrapperbits)
 	$(call if_changed,wrap,cuboot-$*,$(dts))
 
-$(obj)/treeImage.%: vmlinux $(dts) $(wrapperbits)
-	$(call if_changed,wrap,treeboot-$*,$(dts))
-
 $(obj)/treeImage.initrd.%: vmlinux $(dts) $(wrapperbits)
 	$(call if_changed,wrap,treeboot-$*,$(dts),,$(obj)/ramdisk.image.gz)
+
+$(obj)/treeImage.%: vmlinux $(dts) $(wrapperbits)
+	$(call if_changed,wrap,treeboot-$*,$(dts))
 
 $(obj)/zImage:		$(addprefix $(obj)/, $(image-y))
 	@rm -f $@; ln $< $@