V4L/DVB (6136): dvb_frontend: add get_rf_strength function pointer to dvb_tuner_ops

Add get_rf_strength function pointer to dvb_tuner_ops, so that rf signal
strength can be read directly from the tuner driver by the dvb demodulator
driver and / or the analog tuning system.

This is an internal api addition -- userspace is not affected.
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Acked-by: Manu Abraham <manu@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/dvb/dvb-core/dvb_frontend.h

@@ -90,6 +90,7 @@ struct dvb_tuner_ops {
 #define TUNER_STATUS_LOCKED 1
 #define TUNER_STATUS_STEREO 2
 	int (*get_status)(struct dvb_frontend *fe, u32 *status);
+	int (*get_rf_strength)(struct dvb_frontend *fe, u16 *strength);
 
 	/** These are provided seperately from set_params in order to facilitate silicon
 	 * tuners which require sophisticated tuning loops, controlling each parameter seperately. */