V4L/DVB (3303): TDA8290 update

This patch
- works around a bug in the I2C bridge that makes the initialization
  of the TDA10046 fail on recent LifeView cards
- puts the AGC output to tristate in sleep mode. This is necessary for
  recent hybrid cards that switch the AGC via tristateing.

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