mediatek: drop platform_get_bootdev

Now that we got fitblk_get_bootdev in /lib/upgrade/common.sh we don't
need platform_get_bootdev in each of the subtargets any longer.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

target/linux/mediatek/mt7623/base-files/lib/upgrade/platform.sh

@@ -1,20 +1,5 @@
 REQUIRE_IMAGE_METADATA=1
 
-platform_get_bootdev() {
-	local rootdisk="$(cat /sys/firmware/devicetree/base/chosen/rootdisk)"
-	local handle bootdev
-	for handle in /sys/class/block/*/of_node/phandle /sys/class/block/*/device/of_node/phandle; do
-		[ ! -e "$handle" ] && continue
-		if [ "$rootdisk" = "$(cat $handle)" ]; then
-			bootdev="${handle%/of_node/phandle}"
-			bootdev="${bootdev%/device}"
-			bootdev="${bootdev#/sys/class/block/}"
-			echo "$bootdev"
-			break
-		fi
-	done
-}
-
 # Legacy full system upgrade including preloader for MediaTek SoCs on eMMC or SD
 legacy_mtk_mmc_full_upgrade() {
 	local diskdev partdev diff oldrecovery
@@ -100,7 +85,7 @@ platform_do_upgrade() {
 	unielec,u7623-02)
 		[ -e /dev/fit0 ] && fitblk /dev/fit0
 		[ -e /dev/fitrw ] && fitblk /dev/fitrw
-		bootdev="$(platform_get_bootdev)"
+		bootdev="$(fitblk_get_bootdev)"
 		EMMC_KERN_DEV="/dev/$bootdev"
 		emmc_do_upgrade "$1"
 		;;