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 <[e-mail]>
Signed-off-by: Brian Norris <[e-mail]>

drivers/mtd/onenand/onenand_base.c

···
 			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--;
 	}