staging: bcm2835-audio: Drop DT dependency

Just like the bcm2835-video make this a platform driver which is probed
by vchiq. In order to change the number of channels use a module
parameter instead, but use the maximum as default.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>