MIPS: Add dtbs_install target

Add the dtbs_install Makefile target to install the dtb files into
$INSTALL_DTBS_PATH.
Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Tested-by: Kevin Cernekee <cernekee@gmail.com>
Cc: f.fainelli@gmail.com
Cc: jaedon.shin@gmail.com
Cc: tglx@linutronix.de
Cc: jason@lakedaemon.net
Cc: jogo@openwrt.org
Cc: arnd@arndb.de
Cc: computersforpeace@gmail.com
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/8836/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Makefile

@@ -367,6 +367,10 @@ PHONY += dtbs
 dtbs: scripts
 	$(Q)$(MAKE) $(build)=arch/mips/boot/dts
 
+PHONY += dtbs_install
+dtbs_install:
+	$(Q)$(MAKE) $(dtbinst)=arch/mips/boot/dts
+
 archprepare:
 ifdef CONFIG_MIPS32_N32
 	@echo '  Checking missing-syscalls for N32'
@@ -407,6 +411,7 @@ define archhelp
 	echo '  uImage.lzma          - U-Boot image (lzma)'
 	echo '  uImage.lzo           - U-Boot image (lzo)'
 	echo '  dtbs                 - Device-tree blobs for enabled boards'
+	echo '  dtbs_install         - Install dtbs to $(INSTALL_DTBS_PATH)'
 	echo
 	echo '  These will be default as appropriate for a configured platform.'
 endef