filelock: convert posix_owner_key to take file_lock_core arg

Convert posix_owner_key to take struct file_lock_core pointer, and fix
up the callers to pass one in.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20240131-flsplit-v3-21-c6129007ee8d@kernel.org


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