[media] cx23855: add frontend set voltage function into state

Setting the LNB voltage requires setting some GPIOs on the cx23885 with some boards before calling the actual set_voltage function in the demod driver. Add a function pointer into state for that case.
Signed-off-by: Olli Salonen <olli.salonen@iki.fi>
Acked-by: Antti Palosaari <crope@iki.fi>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/pci/cx23885/cx23885.h

@@ -297,6 +297,8 @@ struct cx23885_tsport {
 	struct i2c_client *i2c_client_tuner;
 
 	int (*set_frontend)(struct dvb_frontend *fe);
+	int (*fe_set_voltage)(struct dvb_frontend *fe,
+				fe_sec_voltage_t voltage);
 };
 
 struct cx23885_kernel_ir {