[][Refactor eMMC image of MT7981]

[Description]
Refactor eMMC image of MT7981.
The whole image format is changed:
 - Kernel and rootfs reside in individual partitions.
 - rootfs_data split from rootfs partition using loop device with offset.
 - Upgrading firmware usig tarball with saving config files supported.
 - No recovery partition needed.
 - No GPT partition offset and size restricted.

Important note:
Please select the following packages to make emmc firmware upgrading work:
e2fsprogs mkf2fs blkid blockdev losetup kmod-fs-ext4 kmod-fs-f2fs

[Release-log]
  N/A

Change-Id: I17ad85efa235d068504eeb848431b0c73ae768b4

Change-Id: Iae56e7776b049d3fd9f79861523379794e99c7f0
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/5374466
diff --git a/target/linux/mediatek/files-5.4/arch/arm64/boot/dts/mediatek/mt7981-sd-rfb.dts b/target/linux/mediatek/files-5.4/arch/arm64/boot/dts/mediatek/mt7981-sd-rfb.dts
index b3db66b..7d0c097 100644
--- a/target/linux/mediatek/files-5.4/arch/arm64/boot/dts/mediatek/mt7981-sd-rfb.dts
+++ b/target/linux/mediatek/files-5.4/arch/arm64/boot/dts/mediatek/mt7981-sd-rfb.dts
@@ -2,11 +2,11 @@
 #include "mt7981.dtsi"
 / {
 	model = "MediaTek MT7981 RFB";
-	compatible = "mediatek,mt7981-emmc-rfb";
+	compatible = "mediatek,mt7981-sd-rfb";
 	chosen {
 		bootargs = "console=ttyS0,115200n1 loglevel=8  \
 				earlycon=uart8250,mmio32,0x11002000 \
-				root=/dev/mmcblk0p7 rootfstype=squashfs,f2fs";
+				root=PARTLABEL=rootfs rootfstype=squashfs,f2fs";
 	};
 
 	memory {