mtd: Delete partitions attached to the device when a device is deleted

If we don't do that, partitions might still be exposed while the
underlying device is gone.

Fixes: 2a74930da57f ("mtd: mtdpart: implement proper partition handling")
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Tested-by: Heiko Schocher <hs@denx.de>
diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 7a15ded..cb7ca38 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -528,6 +528,13 @@
 	struct mtd_notifier *not;
 #endif
 
+	ret = del_mtd_partitions(mtd);
+	if (ret) {
+		debug("Failed to delete MTD partitions attached to %s (err %d)\n",
+		      mtd->name, ret);
+		return ret;
+	}
+
 	mutex_lock(&mtd_table_mutex);
 
 	if (idr_find(&mtd_idr, mtd->index) != mtd) {