MIPS: Add uImage build target

Add a uImage build target for MIPS, which builds uImage.gz (a U-Boot
image of vmlinux.bin.gz), and then symlinks it to uImage. This allows
for the use of other compression algorithms in future, and is how a few
other architectures do it.

It's enabled conditionally on load-y >= 0xffffffff80000000 which
hopefully allows 64bit kernels to also work as long as the load and
entry address can be represented by the 32bit addresses in the U-Boot
image format.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5795/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index 91d5baa..75a36ad 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -263,6 +263,10 @@
 boot-y			:= vmlinux.bin
 boot-y			+= vmlinux.ecoff
 boot-y			+= vmlinux.srec
+ifeq ($(shell expr $(load-y) \< 0xffffffff80000000 2> /dev/null), 0)
+boot-y			+= uImage
+boot-y			+= uImage.gz
+endif
 
 # compressed boot image targets (arch/mips/boot/compressed/)
 bootz-y			:= vmlinuz
@@ -341,6 +345,8 @@
 	echo '  vmlinuz.ecoff        - ECOFF zboot image'
 	echo '  vmlinuz.bin          - Raw binary zboot image'
 	echo '  vmlinuz.srec         - SREC zboot image'
+	echo '  uImage               - U-Boot image'
+	echo '  uImage.gz            - U-Boot image (gzip)'
 	echo
 	echo '  These will be default as appropriate for a configured platform.'
 endef