btrfs: remove unused pointer inode in relink_file_extents

Pointer inode is being assigned but is never used hence it is redundant
and can be removed. It's been unused since the introduction in
38c227d8 ("Btrfs: snapshot-aware defrag").

Cleans up clang warning:

  variable ‘inode’ set but not used [-Wunused-but-set-variable]
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -2750,12 +2750,9 @@ static void relink_file_extents(struct new_sa_defrag_extent *new)
 	struct btrfs_path *path;
 	struct sa_defrag_extent_backref *backref;
 	struct sa_defrag_extent_backref *prev = NULL;
-	struct inode *inode;
 	struct rb_node *node;
 	int ret;
 
-	inode = new->inode;
-
 	path = btrfs_alloc_path();
 	if (!path)
 		return;