V4L/DVB (7392): saa7134: support 2nd DVB-S section of the MD8800

There are some restrictions:
- The 2nd DVB-S section will only work if the 1st is configured for DVB-S too.
  so "options saa7134-dvb use_frontend=0,1" won't work.
- Currently it is not possible to set the higher LNB supply voltages, so
  14V instead of 13V in the 2nd section.
- It is not possibe to turn off the 2nd LNB supply independently.
This comes from the problem that the 2nd section can't access the i2c interface
of the LNB supply chip.

Signed-off-by: Hartmut Hackmann <hartmut.hackmann@t-online.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>