mtd: don't lock when recursively deleting partitions

When recursively deleting partitions, don't acquire the masters
partition lock twice. Otherwise the process ends up in a deadlocked
state.

Fixes: 46b5889c ("mtd: implement proper partition handling")
Signed-off-by: David Bauer <mail@david-bauer.net>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210217195320.893253-1-mail@david-bauer.net

drivers/mtd/mtdpart.c

@@ -331,7 +331,7 @@ static int __del_mtd_partitions(struct mtd_info *mtd)
 
 	list_for_each_entry_safe(child, next, &mtd->partitions, part.node) {
 		if (mtd_has_partitions(child))
-			del_mtd_partitions(child);
+			__del_mtd_partitions(child);
 
 		pr_info("Deleting %s MTD partition\n", child->name);
 		ret = del_mtd_device(child);