staging: vc04_services: bcm2835-audio: Use vchi_msg_hold()

vchi_msg_dequeue() provides the same functionality as vchi_msg_hold()
except it copies the message data as opposed to the later which provides
the data in place.

The copying is done on a local variable, so there is no need to keep the
message out the function's bounds, so use vchi_msg_hold() instead.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/20200629150945.10720-14-nsaenzjulienne@suse.de


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