recovery-initramfs: get rid off singlemtdsys variable

This variable is not defined in ccmp1 platforms, making the
swupdate for single mtd failing.

Instead of reading this variable from uboot environment,
determine if the system is multimtd checking the existence
of /dev/ubi1.

Signed-off-by: Francisco Gil <francisco.gilmartinez@digi.com>

meta-digi-dey/recipes-core/recovery/recovery-initramfs/recovery-initramfs-init

@@ -231,10 +231,8 @@ format_ubi_volume() {
 	psplash_message "Formatting '${1}' partition..."
 	psplash_progress "0"
 
-	# Read the singlemtdsys variable.
-	read_uboot_var singlemtdsys singlemtdsys
-
-	if [ "${singlemtdsys}" = "yes" ]; then
+	# If /dev/ubi1 exists is a system with multiple MTD partitions
+	if [ ! -c "/dev/ubi1" ]; then
 		# Find the volume number associated to the volume name
 		for d in /dev/ubi0_*; do
 			volname="$(ubinfo ${d} | grep ^Name | awk '{print $(2)}')"