V4L/DVB (5314): Added support for tda827x tuners with preamlifiers

This patch contains
- new tuning code for the tda827xa silicon tuner.
- controls the preamplifier of some boards with this tuner.
- support for the Philips Tiger S hybrid DVB-T reference design.
- reworked the saa7134-dvb modulue to get rid of most of the
  small board specific functions.

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