mtd: silence some uninitialized variable warnings

The "tmp_retlen" variable can be uninitialized if action() fails.  It's
harmless except for the static checker warning.  I have moved the error
handling earlier to fix it.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/onenand/onenand_base.c

@@ -3188,13 +3188,13 @@ static int onenand_otp_walk(struct mtd_info *mtd, loff_t from, size_t len,
 			size_t tmp_retlen;
 
 			ret = action(mtd, from, len, &tmp_retlen, buf);
+			if (ret)
+				break;
 
 			buf += tmp_retlen;
 			len -= tmp_retlen;
 			*retlen += tmp_retlen;
 
-			if (ret)
-				break;
 		}
 		otp_pages--;
 	}