compositor-openwfd: Use wfd_device_id as drm fd

owfdrm uses non-0 (0 == WFD_INVALID_DEVICE_ID) fd's as wfd_device_ids.
This is not standardized, but also not invalid.

compositor/compositor-openwfd.c

@@ -111,7 +111,7 @@ init_egl(struct wfd_compositor *ec)
 		EGL_NONE
 	};
 
-	fd = wfdDeviceGetDRMfd(ec->dev);
+	fd = wfdGetDeviceAttribi(ec->dev, WFD_DEVICE_ID);
 	if (fd < 0)
 		return -1;