[media] cx231xx-core: fix GPIO comments

The number of the cx231xx REQ for GPIO register set/get are wrong.
They should follow what's there at cx231xx-pcb-cfg.h.

Noticed while checking the cx231xx parser at the v4l-utils.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>