btrfs-progs: check: Fix false alert about uninitialized variable

GCC 8.2.1 will report the following error:

  check/main.c: In function 'try_repair_inode':
  check/main.c:2606:5: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
    if (!ret) {
       ^
  check/main.c:2584:6: note: 'ret' was declared here
    int ret;
        ^~~

The offending code is in repair_mismatch_dir_hash():

	int ret;

	printf(
	"Deleting bad dir items with invalid hash for root %llu ino %llu\n",
		root->root_key.objectid, rec->ino);
	while (!list_empty(&rec->mismatch_dir_hash)) {
		/* do some repair */
	}
	if (!ret) { <<< Here
		/* do some fix */
	}

The truth is, to enter try_repair_inode(), we must have
I_ERR_MISMATCH_DIR_HASH bit set for rec->errors.

And just after we set I_ERR_MISMATCH_DIR_HASH, we call
add_mismatch_dir_hash() and handled its error correctly.

So it's impossible to to skip the while loop.

Fix it by initializing @ret to -EUCLEAN, so even we hit some impossible
case, repair_mismatch_dir_hash() won't falsely consider the mismatch
hash fixed.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

check/main.c

@@ -2663,7 +2663,7 @@ static int repair_mismatch_dir_hash(struct btrfs_trans_handle *trans,
 				    struct inode_record *rec)
 {
 	struct mismatch_dir_hash_record *hash;
-	int ret;
+	int ret = -EUCLEAN;
 
 	printf(
 	"Deleting bad dir items with invalid hash for root %llu ino %llu\n",