staging: vchiq_arm: Add a matching unregister call

All the registered children of vchiq have a corresponding call to
platform_device_unregister except bcm2835_audio. Fix that.

Fixes: 25c7597a ("staging: vchiq_arm: Register a platform device for audio")

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/20200629150945.10720-9-nsaenzjulienne@suse.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>