charlotte: Mount system partition to /system_root and /system

to fix flashing gapps

Change-Id: I3dc124707a1868b36d5f650850caf6c98f128c69

recovery.fstab

@@ -8,6 +8,7 @@
 /odm               ext4      /dev/block/platform/ff3c0000.ufs/by-name/odm               flags=display="ODM";backup=1
 /data              f2fs      /dev/block/platform/ff3c0000.ufs/by-name/userdata          flags=display="Data";backup=1;length=-16384;fileencryption=aes-256-xts:aes-256-cts;encryptable=/dev/block/platform/ff3c0000.ufs/by-name/encrypt
 /system            ext4      /dev/block/platform/ff3c0000.ufs/by-name/system            flags=display="System";backup=1
+/system_root       ext4      /dev/block/platform/ff3c0000.ufs/by-name/system            flags=display="System";backup=0
 /system_image      emmc      /dev/block/platform/ff3c0000.ufs/by-name/system            flags=display="System image";backup=1
 /vendor            ext4      /dev/block/platform/ff3c0000.ufs/by-name/vendor            flags=display="Vendor";backup=1
 /vendor_image      emmc      /dev/block/platform/ff3c0000.ufs/by-name/vendor            flags=display="Vendor image";backup=1