staging: vchi: Get rid of effect less expression

It was probably there to trick compilers into ignoring unused variables,
which isn't needed in Linux.
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/20200629150945.10720-22-nsaenzjulienne@suse.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/interface/vchiq_arm/vchiq_shim.c

@@ -288,8 +288,6 @@ static struct vchi_service *service_alloc(struct vchiq_instance *instance,
 {
 	struct vchi_service *service = kzalloc(sizeof(struct vchi_service), GFP_KERNEL);
 
-	(void)instance;
-
 	if (service) {
 		if (!vchiu_queue_init(&service->queue, 64)) {
 			service->callback = setup->callback;