kbuild: Rename UIMAGE to MKIMAGE

U-Boot uses the 'mkimage' tool to produce various image types,
not only uImage image type. Rename the invocation name from
UIMAGE to MKIMAGE.

The following command was used to do the replacement:
git grep 'quiet_cmd_mkimage.* = UIMAGE' | cut -d : -f 1 | \
 xargs -i sed -i "s@\(quiet_cmd_mkimage\)\(.*\) = UIMAGE @\1\2 = MKIMAGE@" {}

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Tom Rini <trini@ti.com>
Cc: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/spl/Makefile b/spl/Makefile
index be5fd3b..9f5dbf4 100644
--- a/spl/Makefile
+++ b/spl/Makefile
@@ -171,7 +171,7 @@
 	$(shell $(LD) --version | \
 	  sed -ne 's/GNU ld version \([0-9][0-9]*\)\.\([0-9][0-9]*\).*/-DLD_MAJOR=\1 -DLD_MINOR=\2/p')
 
-quiet_cmd_mkimage = UIMAGE  $@
+quiet_cmd_mkimage = MKIMAGE $@
 cmd_mkimage = $(objtree)/tools/mkimage $(MKIMAGEFLAGS_$(@F)) -d $< $@ \
 	$(if $(KBUILD_VERBOSE:1=), >/dev/null)