ath79: use nand_do_upgrade by default for nand subtarget

On nand subtarget, the default upgrade mechanism should be
nand_do_upgrade. This patch changes platform_do_upgrade()
accordingly.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/ath79/nand/base-files/lib/upgrade/platform.sh

@@ -13,13 +13,11 @@ platform_do_upgrade() {
 	local board=$(board_name)
 
 	case "$board" in
-	aerohive,hiveap-121|\
+	glinet,gl-ar300m-nand)
-	netgear,wndr4300|\
+		default_do_upgrade "$1"
-	zyxel,nbg6716)
-		nand_do_upgrade "$1"
 		;;
 	*)
-		default_do_upgrade "$1"
+		nand_do_upgrade "$1"
 		;;
 	esac
 }