mtd: convert remaining users to mtd_device_register()

The older add_mtd_device()/add_mtd_partitions() and their removal
counterparts will soon be gone.  Replace uses with mtd_device_register()
and mtd_device_unregister().

Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/mtd/nand/rtc_from4.c b/drivers/mtd/nand/rtc_from4.c
index 67440b5..c9f9127 100644
--- a/drivers/mtd/nand/rtc_from4.c
+++ b/drivers/mtd/nand/rtc_from4.c
@@ -580,7 +580,8 @@
 #endif
 
 	/* Register the partitions */
-	ret = add_mtd_partitions(rtc_from4_mtd, partition_info, NUM_PARTITIONS);
+	ret = mtd_device_register(rtc_from4_mtd, partition_info,
+				  NUM_PARTITIONS);
 	if (ret)
 		goto err_3;