V4L/DVB (4768): Add the Asus P7131 Dual hybrid to the new tda8290_i2c_gate_ctrl

The gate control was moved to a separate function.

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