ceph: don't allow delegations to be set on directories

ceph: don't allow delegations to be set on directories

With the advent of directory leases, it's necessary to set the
->setlease() handler in directory file_operations to properly deny them.

Fixes: e6d28ebc17eb ("filelock: push the S_ISREG check down to ->setlease handlers")
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260107-setlease-6-19-v1-5-85f034abcc57@kernel.org
Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>