exfat: Fix potential use after free in exfat_load_upcase_table()

This code calls brelse(bh) and then dereferences "bh" on the next line
resulting in a possible use after free.  The brelse() should just be
moved down a line.

Fixes: b676fdbcf4c8 ("exfat: standardize checksum calculation")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

fs/exfat/nls.c

@@ -692,8 +692,8 @@ static int exfat_load_upcase_table(struct super_block *sb,
 				index++;
 			}
 		}
-		brelse(bh);
 		chksum = exfat_calc_chksum32(bh->b_data, i, chksum, CS_DEFAULT);
+		brelse(bh);
 	}
 
 	if (index >= 0xFFFF && utbl_checksum == chksum)