zfs: Set st_rdev to NODEV, not 0, when not a device

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D51954

sys/contrib/openzfs/module/os/freebsd/zfs/zfs_ctldir.c

@@ -494,7 +494,7 @@ zfsctl_common_getattr(vnode_t *vp, vattr_t *vap)
 
 	vap->va_uid = 0;
 	vap->va_gid = 0;
-	vap->va_rdev = 0;
+	vap->va_rdev = NODEV;
 	/*
 	 * We are a purely virtual object, so we have no
 	 * blocksize or allocated blocks.

sys/contrib/openzfs/module/os/freebsd/zfs/zfs_vnops_os.c

@@ -2013,7 +2013,7 @@ zfs_getattr(vnode_t *vp, vattr_t *vap, int flags, cred_t *cr)
 	if (vp->v_type == VBLK || vp->v_type == VCHR)
 		vap->va_rdev = zfs_cmpldev(rdev);
 	else
-		vap->va_rdev = 0;
+		vap->va_rdev = NODEV;
 	vap->va_gen = zp->z_gen;
 	vap->va_flags = 0;	/* FreeBSD: Reset chflags(2) flags. */
 	vap->va_filerev = zp->z_seq;