sinowealth-nubwo: fix implicit declaration of function ‘vasprintf’

driver-sinowealth-nubwo.c was missing to include "config.h" so
_GNU_SOURCE wasn't defined soon enough.

Co-authored-by: Elián Hanisch <elian.hanisch@ing.unlp.edu.ar>

src/driver-sinowealth-nubwo.c

@@ -21,6 +21,7 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
+#include "config.h"
 #include "libratbag-enums.h"
 #include "libratbag-hidraw.h"
 #include "libratbag-private.h"