pbio/platform/prime_hub: set usb product name
This helps us find the hub in pybricksdev
#define USBD_PID 0x5740
#define USBD_LANGID_STRING 0x409
#define USBD_MANUFACTURER_STRING "STMicroelectronics"
-#define USBD_PRODUCT_FS_STRING "STM32 Virtual ComPort in FS Mode"
+#define USBD_PRODUCT_FS_STRING "Pybricks Hub"
#define USBD_CONFIGURATION_FS_STRING "VCP Config"
#define USBD_INTERFACE_FS_STRING "VCP Interface"
