staging: unisys: visornic: Remove unnecessary return values

Removes unnecessary return value in send_rcv_posts_if_needed(), since
NAPI polling functions do not return errors.

Signed-off-by: David Binder <david.binder@unisys.com>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Reviewed-by: Tim Sell <timothy.sell@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>