filelock: add lease_dispose_list() helper

filelock: add lease_dispose_list() helper

The lease-handling code paths always know they're disposing of leases,
yet locks_dispose_list() checks flags at runtime to determine whether
to call locks_free_lease() or locks_free_lock().

Split out a dedicated lease_dispose_list() helper for lease code paths.
This makes the type handling explicit and prepares for the upcoming
lease_manager enhancements where lease-specific operations are being
consolidated.

Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20251204-dir-deleg-ro-v2-1-22d37f92ce2c@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>