kernel/base-files: clean up old code related to refreshing mtd partitions, it is no longer used anywhere

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 37282

target/linux/x86/base-files/lib/upgrade/platform.sh

@@ -1,5 +1,3 @@
-USE_REFRESH=1
-
 x86_get_rootfs() {
 	local rootfsdev
 	local rootfstype
@@ -27,10 +25,6 @@ platform_check_image() {
 	esac
 }
 
-platform_refresh_partitions() {
-	return 0
-}
-
 platform_copy_config() {
 	local rootfs="$(x86_get_rootfs)"
 	local rootfsdev="${rootfs##*:}"