Add support for HID over SPI (#486)

This adds (or more accurately completes, since it was already started) support for HID over SPI devices.
Handling is almost identical to HID over I2C.

linux/hid.c

@@ -593,6 +593,7 @@ static struct hid_device_info * create_device_info_for_device(struct udev_device
 		case BUS_BLUETOOTH:
 		case BUS_I2C:
 		case BUS_USB:
+		case BUS_SPI:
 			break;
 
 		default:
@@ -681,6 +682,14 @@ static struct hid_device_info * create_device_info_for_device(struct udev_device
 
 			break;
 
+		case BUS_SPI:
+			cur_dev->manufacturer_string = wcsdup(L"");
+			cur_dev->product_string = utf8_to_wchar_t(product_name_utf8);
+
+			cur_dev->bus_type = HID_API_BUS_SPI;
+
+			break;
+
 		default:
 			/* Unknown device type - this should never happen, as we
 			 * check for USB and Bluetooth devices above */