Some saa7134 devices require to open an i2c gate before tuning. This
patch fix the initialization for those devices.

The nxt200x_gate_ctrl() logic were returned back to the old place, since
we don't know how to close the gate. A future pacth could revert that
change and provide the proper close gate control, to avoid keeping it
open forever.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>