treewide: replace /sys/devices/virtual/ubi by /sys/class/ubi

Starting from Linux Kernel version 6.3 UBI devices will no longer be
considered virtual, but rather have an MTD device parent. Hence they
will no longer be listed under /sys/devices/virtual/ubi which is
used in multiple places in OpenWrt. Prepare for future kernels by
using /sys/class/ubi instead of /sys/devuces/virtual/ubi.

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

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

@@ -28,7 +28,7 @@ ubi_mknod() {
 
 nand_find_volume() {
 	local ubidevdir ubivoldir
-	ubidevdir="/sys/devices/virtual/ubi/$1"
+	ubidevdir="/sys/class/ubi/"
 	[ ! -d "$ubidevdir" ] && return 1
 	for ubivoldir in $ubidevdir/${1}_*; do
 		[ ! -d "$ubivoldir" ] && continue
@@ -41,13 +41,12 @@ nand_find_volume() {
 }
 
 nand_find_ubi() {
-	local ubidevdir ubidev mtdnum
+	local ubidevdir ubidev mtdnum cmtdnum
 	mtdnum="$( find_mtd_index $1 )"
 	[ ! "$mtdnum" ] && return 1
-	for ubidevdir in /sys/devices/virtual/ubi/ubi*; do
-		[ ! -d "$ubidevdir" ] && continue
+	for ubidevdir in /sys/class/ubi/ubi*; do
+		[ ! -e "$ubidevdir/mtd_num" ] && continue
 		cmtdnum="$( cat $ubidevdir/mtd_num )"
-		[ ! "$mtdnum" ] && continue
 		if [ "$mtdnum" = "$cmtdnum" ]; then
 			ubidev=$( basename $ubidevdir )
 			ubi_mknod "$ubidevdir"