filelock: remove temporary compatibility macros

Everything has been converted to access fl_core fields directly, so we
can now drop these.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20240131-flsplit-v3-46-c6129007ee8d@kernel.org


Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>