fusefs: remove the obsolete rename_lock

This lock was included in the original GSoC submission.  Its purpose
seems to have been to prevent concurrent FUSE_RENAME operations for the
current mountpoint, as well as to synchronize FUSE_RENAME with
fuse_vnode_setparent.  But it's obsolete, now that ef6ea91593 added
mnt_renamelock .

MFC after:	2 weeks
Sponsored by:	ConnectWise
Reviewed by:	kib
Differential Revision: https://reviews.freebsd.org/D55231

sys/fs/fuse/fuse_ipc.c

@@ -550,7 +550,6 @@ fdata_alloc(struct cdev *fdev, struct ucred *cred)
 	TAILQ_INIT(&data->aw_head);
 	data->daemoncred = crhold(cred);
 	data->daemon_timeout = FUSE_DEFAULT_DAEMON_TIMEOUT;
-	sx_init(&data->rename_lock, "fuse rename lock");
 	data->ref = 1;
 
 	return data;
@@ -565,7 +564,6 @@ fdata_trydestroy(struct fuse_data *data)
 		return;
 
 	/* Driving off stage all that stuff thrown at device... */
-	sx_destroy(&data->rename_lock);
 	crfree(data->daemoncred);
 	mtx_destroy(&data->aw_mtx);
 	knlist_delete(&data->ks_rsel.si_note, curthread, 0);

sys/fs/fuse/fuse_ipc.h

@@ -194,8 +194,6 @@ struct fuse_data {
 	 */
 	u_long				ticketer;
 
-	struct sx			rename_lock;
-
 	uint32_t			fuse_libabi_major;
 	uint32_t			fuse_libabi_minor;
 

sys/fs/fuse/fuse_vnops.c

@@ -2272,7 +2272,6 @@ fuse_vnop_rename(struct vop_rename_args *ap)
 		if (err)
 			goto out;
 	}
-	sx_xlock(&data->rename_lock);
 	err = fuse_internal_rename(fdvp, fcnp, tdvp, tcnp);
 	if (err == 0) {
 		if (tdvp != fdvp)
@@ -2280,7 +2279,6 @@ fuse_vnop_rename(struct vop_rename_args *ap)
 		if (tvp != NULL)
 			fuse_vnode_setparent(tvp, NULL);
 	}
-	sx_unlock(&data->rename_lock);
 
 	if (tvp != NULL && tvp != fvp) {
 		cache_purge(tvp);