btrfs: remove redundant initialization of variables in log_new_ancestors

The variables leaf and slot are initialized when declared but the values
assigned to them are never read as they are being re-assigned later on.
The initializations are redundant and can be removed. Cleans up clang
scan build warnings:

fs/btrfs/tree-log.c:6797:25: warning: Value stored to 'leaf' during its
initialization is never read [deadcode.DeadStores]
fs/btrfs/tree-log.c:6798:7: warning: Value stored to 'slot' during its
initialization is never read [deadcode.DeadStores]

It's been there since b8aa330d ("Btrfs: improve performance on fsync
of files with multiple hardlinks") without any usage so it's safe to be
removed.
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/tree-log.c

@@ -6794,8 +6794,8 @@ static int log_new_ancestors(struct btrfs_trans_handle *trans,
 
 	while (true) {
 		struct btrfs_fs_info *fs_info = root->fs_info;
-		struct extent_buffer *leaf = path->nodes[0];
-		int slot = path->slots[0];
+		struct extent_buffer *leaf;
+		int slot;
 		struct btrfs_key search_key;
 		struct inode *inode;
 		u64 ino;