staging: vchiq: Fix an uninitialized variable

Smatch complains that "userdata" can be passed to vchiq_bulk_transfer()
without being initialized.  This leads to a potential information leak
later on.

Fixes: a4367cd2 ("staging: vchiq: convert compat bulk transfer")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20200930123036.GC4282@kadamSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

@@ -952,7 +952,7 @@ static int vchiq_irq_queue_bulk_tx_rx(struct vchiq_instance *instance,
 {
 	struct vchiq_service *service;
 	struct bulk_waiter_node *waiter = NULL;
-	void *userdata;
+	void *userdata = NULL;
 	int status = 0;
 	int ret;