treewide: move nand_do_upgrade call to platform_do_upgrade

Calling nand_do_upgrade() from platform_pre_upgrade() was deprecated
with 30f61a34b4 ("base-files: always use staged sysupgrade").

Update the platform upgrade code to use platform_do_upgrade() for NAND
images as well.

Signed-off-by: Mathias Kresin <dev@kresin.me>

target/linux/lantiq/base-files/lib/upgrade/platform.sh

@@ -5,14 +5,15 @@ platform_check_image() {
 	return 0
 }
 
-platform_pre_upgrade() {
+platform_do_upgrade() {
 	local board=$(board_name)
 
 	case "$board" in
 	bt,homehub-v2b|bt,homehub-v3a|bt,homehub-v5a|zyxel,p-2812hnu-f1|zyxel,p-2812hnu-f3)
 		nand_do_upgrade $1
 		;;
+	*)
+		default_do_upgrade "$ARGV"
+		;;
 	esac
 }
-
-# use default for platform_do_upgrade()