base-files: sysupgrade: support additional mtd options

Add support for passing additional parameters to mtd called during
sysupgrade. It will be required to toggle the "recovery moe" flag
supported by recent tp-link boards.

Signed-off-by: David Bauer <mail@david-bauer.net>
[split code from board support patch; add commit message]
Signed-off-by: Mathias Kresin <dev@kresin.me>

package/base-files/files/lib/upgrade/common.sh

@@ -223,9 +223,9 @@ indicate_upgrade() {
 default_do_upgrade() {
 	sync
 	if [ "$SAVE_CONFIG" -eq 1 ]; then
-		get_image "$1" "$2" | mtd $MTD_CONFIG_ARGS -j "$CONF_TAR" write - "${PART_NAME:-image}"
+		get_image "$1" "$2" | mtd $MTD_ARGS $MTD_CONFIG_ARGS -j "$CONF_TAR" write - "${PART_NAME:-image}"
 	else
-		get_image "$1" "$2" | mtd write - "${PART_NAME:-image}"
+		get_image "$1" "$2" | mtd $MTD_ARGS write - "${PART_NAME:-image}"
 	fi
 	[ $? -ne 0 ] && exit 1
 }

package/base-files/files/sbin/sysupgrade

@@ -4,6 +4,7 @@
 . /lib/functions/system.sh
 
 # initialize defaults
+export MTD_ARGS=""
 export MTD_CONFIG_ARGS=""
 export INTERACTIVE=0
 export VERBOSE=1