Kbuild: centralize MKIMAGE and cmd_uimage definitions

All ARCHs have the same definition of MKIMAGE. Move it to Makefile.lib
to avoid duplication.

All ARCHs have similar definitions of cmd_uimage. Place a sufficiently
parameterized version in Makefile.lib to avoid duplication.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Tested-by: Mike Frysinger <vapier@gentoo.org> [Blackfin]
Tested-by: Michal Simek <monstr@monstr.eu> [Microblaze]
Tested-by: Guan Xuetao <gxt@mprc.pku.edu.cn> [unicore32]
Signed-off-by: Michal Marek <mmarek@suse.cz>

arch/avr32/boot/images/Makefile

@@ -6,8 +6,6 @@
 # for more details.
 #
 
-MKIMAGE		:= $(srctree)/scripts/mkuboot.sh
-
 extra-y		:= vmlinux.bin vmlinux.gz
 
 OBJCOPYFLAGS_vmlinux.bin := -O binary -R .note.gnu.build-id
@@ -17,10 +15,9 @@ $(obj)/vmlinux.bin: vmlinux FORCE
 $(obj)/vmlinux.gz: $(obj)/vmlinux.bin FORCE
 	$(call if_changed,gzip)
 
-quiet_cmd_uimage = UIMAGE $@
-      cmd_uimage = $(CONFIG_SHELL) $(MKIMAGE) -A avr32 -O linux -T kernel	\
-		-C gzip -a $(CONFIG_LOAD_ADDRESS) -e $(CONFIG_ENTRY_ADDRESS)	\
-		-n 'Linux-$(KERNELRELEASE)' -d $< $@
+UIMAGE_LOADADDR = $(CONFIG_LOAD_ADDRESS)
+UIMAGE_ENTRYADDR = $(CONFIG_ENTRY_ADDRESS)
+UIMAGE_COMPRESSION = gzip
 
 targets += uImage uImage.srec
 $(obj)/uImage: $(obj)/vmlinux.gz