Btrfs: get rid of btrfs_symlink_aops

Btrfs: get rid of btrfs_symlink_aops

The only aops we define for symlinks are identical to the aops for
regular files. This has been the case since symlink support was added in
commit 2b8d99a723a3 ("Btrfs: symlinks and hard links"). As far as I can
tell, there wasn't a good reason to have separate aops then, and there
isn't now, so let's just do what most other filesystems do and reuse the
same structure.

Signed-off-by: Omar Sandoval <[email protected]>
Reviewed-by: Nikolay Borisov <[email protected]>
Reviewed-by: David Sterba <[email protected]>
Signed-off-by: David Sterba <[email protected]>