staging: bcm2835-audio: reorder variable declarations & remove trivial comments

When it comes to declaring variables it's preferred, when possible, to
use an inverted tree organization scheme.

Also, removes some comments that were useless.

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