media: tuner-simple: allow setting mono radio mode

For some types of tuners (Philips FMD1216ME(X) MK3 currently) we know that
letting TDA9887 output port 1 remain high (inactive) will switch FM radio
to mono mode.
Let's make use of this functionality - nothing changes for the default
stereo radio mode.

Tested on a Medion 95700 board which has a FMD1216ME tuner.
Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/tuners/tuner-simple.c

@@ -670,6 +670,7 @@ static int simple_set_radio_freq(struct dvb_frontend *fe,
 	int rc, j;
 	struct tuner_params *t_params;
 	unsigned int freq = params->frequency;
+	bool mono = params->audmode == V4L2_TUNER_MODE_MONO;
 
 	tun = priv->tun;
 
@@ -736,8 +737,8 @@ static int simple_set_radio_freq(struct dvb_frontend *fe,
 			config |= TDA9887_PORT2_ACTIVE;
 		if (t_params->intercarrier_mode)
 			config |= TDA9887_INTERCARRIER;
-/*		if (t_params->port1_set_for_fm_mono)
-			config &= ~TDA9887_PORT1_ACTIVE;*/
+		if (t_params->port1_set_for_fm_mono && mono)
+			config &= ~TDA9887_PORT1_ACTIVE;
 		if (t_params->fm_gain_normal)
 			config |= TDA9887_GAIN_NORMAL;
 		if (t_params->radio_if == 2)