common: use get_nand_dev_by_index()

As part of preparation for nand DM conversion the new API has been
introduced to remove direct access to nand_info array. So, use it here
instead of accessing to nand_info array directly.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
diff --git a/common/fb_nand.c b/common/fb_nand.c
index c8c79e9..3d027d4 100644
--- a/common/fb_nand.c
+++ b/common/fb_nand.c
@@ -59,7 +59,7 @@
 		return -EINVAL;
 	}
 
-	*mtd = nand_info[dev->id->num];
+	*mtd = get_nand_dev_by_index(dev->id->num);
 
 	return 0;
 }