treewide: sysupgrade: get rid of platform_nand_pre_upgrade()

1) nand_do_upgrade() is always called by a target code
2) nand_do_upgrade() starts with calling platform_nand_pre_upgrade()

It means there is no need for the platform_nand_pre_upgrade() callback
at all. All code that was present there could bo moved & simplly called
by a target right before the nand_do_upgrade().

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

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

@@ -26,10 +26,7 @@ platform_do_upgrade() {
 	# stage2 directly but need to refactor nand_upgrade_success
 	# for this to work.
 	#   Also the nand functions don't allow url to be used
-	nand_do_upgrade $1
-}
 
-platform_nand_pre_upgrade() {
 	local board=$(board_name)
 
 	case "$board" in
@@ -48,4 +45,6 @@ platform_nand_pre_upgrade() {
 		echo "Upgrading partition $CI_UBIPART (/dev/mtd$(find_mtd_index $CI_UBIPART))"
 		;;
 	esac
+
+	nand_do_upgrade $1
 }