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/rb532/base-files/lib/upgrade/platform.sh

@@ -10,15 +10,11 @@ platform_check_image() {
 	return 0;
 }
 
-platform_pre_upgrade() {
-	nand_do_upgrade "$1"
-}
-
 platform_nand_pre_upgrade() {
 	mtd erase kernel
 	tar xf "$1" "sysupgrade-$(board_name)/kernel" -O | nandwrite -o /dev/mtd0 -
 }
 
 platform_do_upgrade() {
-	default_do_upgrade "$ARGV"
+	nand_do_upgrade "$1"
 }