Add Cavium ThunderX xHCI controller PCI ID

There is an issue with interrupts at the moment, but it works with
polling mode set (hw.usb.xhci.use_polling=1).

Reviewed by:	hselasky
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D3665

sys/dev/usb/controller/xhci_pci.c

@@ -113,6 +113,9 @@ xhci_pci_match(device_t self)
 	case 0x8cb18086:
 		return ("Intel Wildcat Point USB 3.0 controller");
 
+	case 0xa01b177d:
+		return ("Cavium ThunderX USB 3.0 controller");
+
 	default:
 		break;
 	}