staging: vt6656: card.c: Change return of CARDbAddBasicRate to void

In all locations that call this function ignore your returna, so remove
it.

Signed-off-by: Marcos Paulo de Souza <marcos.mage@gmail.com>
Cc: Forest Bond <forest@alittletooquiet.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>