exfat: resolve memory leak from exfat_create_upcase_table()

If exfat_load_upcase_table reaches end and returns -EINVAL,
allocated memory doesn't get freed and while
exfat_load_default_upcase_table allocates more memory, leading to a
memory leak.

Here's link to syzkaller crash report illustrating this issue:
https://syzkaller.appspot.com/text?tag=CrashReport&x=1406c201980000

Reported-by: syzbot+e1c69cadec0f1a078e3d@syzkaller.appspotmail.com
Fixes: a13d1a4d ("exfat: move freeing sbi, upcase table and dropping nls into rcu-delayed helper")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Yang <danielyangkang@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

fs/exfat/nls.c

@@ -779,8 +779,11 @@ int exfat_create_upcase_table(struct super_block *sb)
 				le32_to_cpu(ep->dentry.upcase.checksum));
 
 			brelse(bh);
-			if (ret && ret != -EIO)
+			if (ret && ret != -EIO) {
+				/* free memory from exfat_load_upcase_table call */
+				exfat_free_upcase_table(sbi);
 				goto load_default;
+			}
 
 			/* load successfully */
 			return ret;