Used Avago MGA-81563 RF amplifier could be destroyed pretty easily
with too strong signal or transmitting to bad antenna.
Add module parameter 'enable_rf_gain_ctrl' which allows enabling
RF gain control - otherwise, default without the module parameter,
RF gain control is set to 'grabbed' state which prevents setting
value to the control.
Signed-off-by: NAntti Palosaari <crope@iki.fi>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>