treewide: don't hardcode "sysupgrade.tgz" file name

1) Add BACKUP_FILE and use it when copying an archive to be restored
   after sysupgrade (on the next preinit).
2) Use CONF_TAR for copying backup prepared by the /sbin/sysupgrade

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

target/linux/mvebu/base-files/lib/preinit/79_move_config

@@ -18,7 +18,7 @@ move_config() {
 		esac
 		mkdir -p /boot
 		mount -o rw,noatime "/dev/$partdev" /boot
-		[ -f /boot/sysupgrade.tgz ] && mv -f /boot/sysupgrade.tgz /
+		[ -f "/boot/$BACKUP_FILE" ] && mv -f "/boot/$BACKUP_FILE" /
 		umount /boot
 	fi
 }

target/linux/mvebu/base-files/lib/preinit/81_linksys_syscfg

@@ -4,8 +4,8 @@
 #
 
 preinit_mount_syscfg() {
-
 	. /lib/functions.sh
+	. /lib/upgrade/common.sh
 
 	case $(board_name) in
 	linksys,caiman|linksys,cobra|linksys,mamba|linksys,rango|linksys,shelby|linksys,venom)
@@ -22,12 +22,12 @@ preinit_mount_syscfg() {
 		fi
 		mkdir /tmp/syscfg
 		mount -t ubifs ubi1:syscfg /tmp/syscfg
-		[ -f /tmp/syscfg/sysupgrade.tgz ] && {
+		[ -f "/tmp/syscfg/$BACKUP_FILE" ] && {
 		echo "- config restore -"
 		cd /
-		mv /tmp/syscfg/sysupgrade.tgz /tmp
-		tar xzf /tmp/sysupgrade.tgz
-		rm -f /tmp/sysupgrade.tgz
+		mv "/tmp/syscfg/$BACKUP_FILE" /tmp
+		tar xzf "/tmp/$BACKUP_FILE"
+		rm -f "/tmp/$BACKUP_FILE"
 		sync
 		}
 		;;

target/linux/mvebu/base-files/lib/preinit/82_uDPU

@@ -4,8 +4,8 @@
 #
 
 preinit_mount_udpu() {
-
 	. /lib/functions.sh
+	. /lib/upgrade/common.sh
 
 	case $(board_name) in
 	methode,udpu)
@@ -15,10 +15,10 @@ preinit_mount_udpu() {
 		if [ -b "${mmcdev}p4" ]; then
 			mkdir /misc
 			mount -t f2fs ${mmcdev}p4 /misc
-			[ -f "/misc/sysupgrade.tgz" ] && {
+			[ -f "/misc/$BACKUP_FILE" ] && {
 				echo "- Restoring configuration files -"
-				tar xzf /misc/sysupgrade.tgz -C /
-				rm -f /misc/sysupgrade.tgz
+				tar xzf "/misc/$BACKUP_FILE" -C /
+				rm -f "/misc/$BACKUP_FILE"
 				sync
 			}
 			[ -f "/misc/firmware/recovery.itb" ] && {