[media] rtl2832_sdr: control ADC

Recent rtl28xxu patch I made moved demod ADC enable from power control
to frontend control (due to slave demod support). Because of that we
need call USB interface frontend control too in order to enable ADC.
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/dvb-frontends/rtl2832_sdr.c

@@ -1013,6 +1013,10 @@ static int rtl2832_sdr_start_streaming(struct vb2_queue *vq, unsigned int count)
 	if (s->d->props->power_ctrl)
 		s->d->props->power_ctrl(s->d, 1);
 
+	/* enable ADC */
+	if (s->d->props->frontend_ctrl)
+		s->d->props->frontend_ctrl(s->fe, 1);
+
 	set_bit(POWER_ON, &s->flags);
 
 	ret = rtl2832_sdr_set_tuner(s);
@@ -1064,6 +1068,10 @@ static void rtl2832_sdr_stop_streaming(struct vb2_queue *vq)
 
 	clear_bit(POWER_ON, &s->flags);
 
+	/* disable ADC */
+	if (s->d->props->frontend_ctrl)
+		s->d->props->frontend_ctrl(s->fe, 0);
+
 	if (s->d->props->power_ctrl)
 		s->d->props->power_ctrl(s->d, 0);