rk: arm: support build Image.gz and Image.lz4

Same as arm64.

Change-Id: If129d04388414ba4acd252a274431710ed8d985b
Signed-off-by: Tao Huang <huangtao@rock-chips.com>

arch/arm/Makefile

@@ -315,6 +315,7 @@ archprepare:
 bzImage: zImage
 
 BOOT_TARGETS	= zImage Image xipImage bootpImage uImage
+BOOT_TARGETS	+= Image.gz Image.lz4
 INSTALL_TARGETS	= zinstall uinstall install
 
 PHONY += bzImage $(BOOT_TARGETS) $(INSTALL_TARGETS)

arch/arm/boot/Makefile

@@ -60,6 +60,13 @@ $(obj)/xipImage: FORCE
 $(obj)/Image: vmlinux FORCE
 	$(call if_changed,objcopy)
 
+targets += Image.gz Image.lz4
+$(obj)/Image.gz: $(obj)/Image FORCE
+	$(call if_changed,gzip)
+
+$(obj)/Image.lz4: $(obj)/Image FORCE
+	$(call if_changed,lz4c)
+
 $(obj)/compressed/vmlinux: $(obj)/Image FORCE
 	$(Q)$(MAKE) $(build)=$(obj)/compressed $@