jffs2: add setlease file operation

jffs2: add setlease file operation

Add the setlease file_operation to jffs2_file_operations and
jffs2_dir_operations, pointing to generic_setlease.  A future patch
will change the default behavior to reject lease attempts with -EINVAL
when there is no setlease file operation defined. Add generic_setlease
to retain the ability to set leases on this filesystem.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260108-setlease-6-20-v1-11-ea4dec9b67fa@kernel.org
Acked-by: Richard Weinberger <richard@nod.at>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>