vboxsf: 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: e6d28ebc17 ("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-v1-6-85f034abcc57@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/vboxsf/dir.c

@@ -186,6 +186,7 @@ const struct file_operations vboxsf_dir_fops = {
 	.release = vboxsf_dir_release,
 	.read = generic_read_dir,
 	.llseek = generic_file_llseek,
+	.setlease = simple_nosetlease,
 };
 
 /*