Add nvd alias to nda ndoes.

All ndaX and ndaXpY nodes will appear as nvdX and nvdXpY as well
(through symlinks in devfs via the normal disk aliasing mechanism in
GEOM).

Differential Revision: https://reviews.freebsd.org/D11873

sys/cam/nvme/nvme_da.c

@@ -808,6 +808,10 @@ ndaregister(struct cam_periph *periph, void *arg)
 	    DEVSTAT_ALL_SUPPORTED,
 	    DEVSTAT_TYPE_DIRECT | XPORT_DEVSTAT_TYPE(cpi.transport),
 	    DEVSTAT_PRIORITY_DISK);
+	/*
+	 * Add alias for older nvd drives to ease transition.
+	 */
+	disk_add_alias(disk, "nvd");
 
 	/*
 	 * Acquire a reference to the periph before we register with GEOM.