V4L/DVB (5216): Zl10353: add i2c_gate_ctrl support

Implement I2C gate control for Megasky GL861 and SigmaTek AU6610 support.

Signed-off-by: Chris Pascoe <c.pascoe@itee.uq.edu.au>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>