qualcommax: ipq50xx: sysupgrade: fix OEM UBI volume name for Linksys MX devices

The UBI volume name in OEM firmware for Linksys MX2000, MX5500, and
SPNMX56 is 'squashfs' instead of 'rootfs'. So let's update the volume
accordingly.

Signed-off-by: George Moussalem <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/17968
Signed-off-by: Robert Marko <[email protected]>

target/linux/qualcommax/ipq50xx/base-files/lib/upgrade/platform.sh

@@ -75,7 +75,7 @@ platform_do_upgrade() {
 	linksys,mx2000|\
 	linksys,mx5500|\
 	linksys,spnmx56)
-		remove_oem_ubi_volume rootfs
+		remove_oem_ubi_volume squashfs
 		linksys_mx_do_upgrade "$1"
 		;;
 	*)