V4L/DVB (11700): tda10048: Added option to block i2c gate control from other drivers.

Currently, DVB-T is broken and this fixes it.

The PVRUSB2 has an odd I2C bus configuration where opening the i2c gate
on the digital and analog demod causes the tuner to fail. This needs
to be protected against for the PVRUSB2.

Signed-off-by: Steven Toth <stoth@linuxtv.org>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>