V4L/DVB (8609): media: Clean up platform_driver_unregister() bogosity.

So, platform_driver_unregister() doesn't actually have a return value,
nor do any of the void __exit routines. It's reassuring to know that
people copy and paste blindly. This completely blew up my compiler.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>