[media] dvb-usb-gp8psk: Fix driver name

This patch updates the name of the dvb-usb-gp8psk driver
from "Genpix 8psk-to-USB2 DVB-S" to "Genpix DVB-S".
The old name doesn't reflect newer devices such as the
Skywalker line which also user this driver.

Signed-off-by: Derek Kelly <user.vdr@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>