V4L/DVB (7934): cx18: move gpio_dir/val statics to the cx18 struct.

The gpio_dir/val statics cannot be global, they are card-specific.

Thanks to Andy Walls for pointing this out.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>