mtd: physmap_of: error checking to prevent a NULL pointer dereference

This patch solves a NULL pointer dereference, this may occur if the tuple
is not mappable (jumps to continue in the for-loop). Out of the loop
possible results are:
- info->list_size == 0  if no of the tuples is mappable
- info->list_size == 1
- info->list_size > 1
If no one of the supplied tuples is mappable (info->list_size == 0) and
info->cmtd will not be set. But it is used in mtd_device_parse_register, OOPS!
actually it should generate an error in this case!
Signed-off-by: Anton Prins <anton.prins@nl.bosch.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

drivers/mtd/maps/physmap_of.c

@@ -285,6 +285,7 @@ static int of_flash_probe(struct platform_device *dev)
 	}
 
 	err = 0;
+	info->cmtd = NULL;
 	if (info->list_size == 1) {
 		info->cmtd = info->list[0].mtd;
 	} else if (info->list_size > 1) {
@@ -293,9 +294,10 @@ static int of_flash_probe(struct platform_device *dev)
 		 */
 		info->cmtd = mtd_concat_create(mtd_list, info->list_size,
 					       dev_name(&dev->dev));
+	}
 	if (info->cmtd == NULL)
 		err = -ENXIO;
-	}
+
 	if (err)
 		goto err_out;