[media] e4000: get rid of DVB i2c_gate_ctrl()

Gate control is now implemented by rtl2832 I2C adapter so we do not
need proprietary DVB i2c_gate_ctrl() anymore.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>