staging: bcm2835-camera: Unify header inclusion defines

Most of the headers use ifndef FOO_H, whilst mmal-parameters.h
used ifndef __FOO_H.

Revise mmal-parameters.h to drop the underscores and make the
headers all consistent.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>