staging: vchiq: Fix bulk userdata handling

The addition of the local 'userdata' pointer to
vchiq_irq_queue_bulk_tx_rx omitted the case where neither BLOCKING nor
WAITING modes are used, in which case the value provided by the
caller is replaced with a NULL.

Fixes: 4184da4 ("staging: vchiq: fix __user annotations")

Signed-off-by: Phil Elwell <phil@raspberrypi.com>

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

@@ -961,7 +961,7 @@ static int vchiq_irq_queue_bulk_tx_rx(struct vchiq_instance *instance,
 	struct vchiq_service *service;
 	struct bulk_waiter_node *waiter = NULL;
 	bool found = false;
-	void *userdata = NULL;
+	void *userdata;
 	int status = 0;
 	int ret;
 
@@ -1000,6 +1000,8 @@ static int vchiq_irq_queue_bulk_tx_rx(struct vchiq_instance *instance,
 			"found bulk_waiter %pK for pid %d", waiter,
 			current->pid);
 		userdata = &waiter->bulk_waiter;
+	} else {
+		userdata = args->userdata;
 	}
 
 	/*