[media] v4l: add control for RF tuner PLL lock flag

Add volatile boolean control to indicate if tuner frequency synthesizer
is locked to requested frequency. That means tuner is able to receive
given frequency. Control is named as "PLL lock", since frequency
synthesizers are based of phase-locked-loop. Maybe more general name
could be wise still?

Cc: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
index 405279f..2ac5597 100644
--- a/include/uapi/linux/v4l2-controls.h
+++ b/include/uapi/linux/v4l2-controls.h
@@ -912,5 +912,6 @@
 #define V4L2_CID_RF_TUNER_MIXER_GAIN		(V4L2_CID_RF_TUNER_CLASS_BASE + 52)
 #define V4L2_CID_RF_TUNER_IF_GAIN_AUTO		(V4L2_CID_RF_TUNER_CLASS_BASE + 61)
 #define V4L2_CID_RF_TUNER_IF_GAIN		(V4L2_CID_RF_TUNER_CLASS_BASE + 62)
+#define V4L2_CID_RF_TUNER_PLL_LOCK			(V4L2_CID_RF_TUNER_CLASS_BASE + 91)
 
 #endif