[media] em28xx: support for 2304:0242 PCTV QuatroStick (510e)

It is mostly copy/paste of the 520e code with setting GPIO7 removed
(no LED light).

I've worked on just released vanilla linux-3.3.0 kernel, so there may
be 1/2 lines offset to the internal working source, but most of the
code should apply cleanly.

I was able to get the DVB-C working (tuned and watched TV). Haven't
tested DVB-T (no signal atm).

Special thanks to everybody who worked on the code and to Antti
Palosaari and Devin Heitmueller who provided essential support on irc.

Hardware is based of:
Empia EM2884
Micronas DRX 3926K
NXP TDA18271HDC2
AVF4910 (not used atm)

Signed-off-by: Ivan Kalvachev <ikalvachev@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>