drv/usb/stm32_usbd: use Pybricks class/subclass/protocol

This adds new defines for the Pybricks USB device class, subclass and
protocol. The class (0xff) is defined by the USB-IF and is the vendor-
specific class. The subclass and protocol are vendor-specific and come
from the first two bytes of the the Pybricks Bluetooth UUIDs.

This allows us to identify hubs running Pybricks when enumerating USB
devices.

lib/pbio/drv/usb/stm32_usbd/usbd_desc.c

@@ -47,6 +47,7 @@
 #include <lego_usb.h>
 
 #include <pbdrv/config.h>
+#include <pbio/protocol.h>
 
 #include "usbd_core.h"
 #include "usbd_conf.h"
@@ -73,9 +74,9 @@ uint8_t USBD_DeviceDesc[USB_LEN_DEV_DESC] __ALIGN_END = {
     USB_DESC_TYPE_DEVICE,     /* bDescriptorType */
     0x00,                     /* bcdUSB */
     0x02,
-    0x02,                     /* bDeviceClass */
-    0x02,                     /* bDeviceSubClass */
-    0x00,                     /* bDeviceProtocol */
+    PBIO_PYBRICKS_USB_DEVICE_CLASS,     /* bDeviceClass */
+    PBIO_PYBRICKS_USB_DEVICE_SUBCLASS,  /* bDeviceSubClass */
+    PBIO_PYBRICKS_USB_DEVICE_PROTOCOL,  /* bDeviceProtocol */
     USB_MAX_EP0_SIZE,         /* bMaxPacketSize */
     LOBYTE(PBDRV_CONFIG_USB_VID), /* idVendor */
     HIBYTE(PBDRV_CONFIG_USB_VID), /* idVendor */

lib/pbio/include/pbio/protocol.h

@@ -311,6 +311,13 @@ extern const uint8_t pbio_nus_service_uuid[];
 extern const uint8_t pbio_nus_rx_char_uuid[];
 extern const uint8_t pbio_nus_tx_char_uuid[];
 
+/** USB bDeviceClass for Pybricks hubs */
+#define PBIO_PYBRICKS_USB_DEVICE_CLASS 0xFF
+/** USB bDeviceSubClass for Pybricks hubs */
+#define PBIO_PYBRICKS_USB_DEVICE_SUBCLASS 0xC5
+/** USB bDeviceProtocol for Pybricks hubs */
+#define PBIO_PYBRICKS_USB_DEVICE_PROTOCOL 0xF5
+
 #endif // _PBIO_PROTOCOL_H_
 
 /** @} */