treewide: when copying a backup file always specify dest name

$CONF_TAR shouldn't be assumed to always point to the sysupgrade.tgz.
This change makes code more generic and allows refactoring $CONF_TAR.

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

target/linux/mvebu/base-files/lib/upgrade/linksys.sh

@@ -93,6 +93,6 @@ platform_do_upgrade_linksys() {
 }
 
 platform_copy_config_linksys() {
-	cp -f "$CONF_TAR" /tmp/syscfg/
+	cp -f "$CONF_TAR" "/tmp/syscfg/$BACKUP_FILE"
 	sync
 }

target/linux/mvebu/base-files/lib/upgrade/sdcard.sh

@@ -106,7 +106,7 @@ platform_copy_config_sdcard() {
 	if export_partdevice partdev 1; then
 		mkdir -p /boot
 		[ -f /boot/kernel.img ] || mount -o rw,noatime /dev/$partdev /boot
-		cp -af "$CONF_TAR" /boot/
+		cp -af "$CONF_TAR" "/boot/$BACKUP_FILE"
 		sync
 		umount /boot
 	fi

target/linux/mvebu/base-files/lib/upgrade/uDPU.sh

@@ -150,7 +150,7 @@ platform_do_upgrade_uDPU() {
 platform_copy_config_uDPU() {
 	# Config is saved on the /misc partition and copied on the rootfs after the reboot
 	if [ -f "$CONF_TAR" ]; then
-		cp -f "$CONF_TAR" /misc
+		cp -f "$CONF_TAR" "/misc/$BACKUP_FILE"
 		sync
 	fi
 }