staging: bcm2835-audio: rename platform_driver structure

It was called bcm2835_alsa0_driver, that "0" didn't mean much.

Suggested-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>