V4L/DVB (4479): LNB voltage control was inverted for the benefit of geniatech cards...

1) It sets LNBDCPol differently based on the card type. Now it should
work properly for both the kworld and geniatech cards.
2) It stops returning an error for the SEC_VOLTAGE_OFF voltage command
(the cx88-dvb level handles the actual voltage on/off, but it still
passes the ioctl down to the cx24123 level, which previously rejected
the OFF as invalid so the ioctl would report failure)

Acked-by: Manu Abraham <manu@linuxtv.org>
Signed-off-by: Yeasah Pell <yeasah@schwide.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>