[media] cx231xx: fix tuner compliance issues

The g_tuner call wasn't passed on to the subdevices, g_frequency didn't
check for invalid tuners and a low-level function that was expected to
return 0 or a negative error returned a positive number instead, causing
s_frequency to return bogus errors.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/usb/cx231xx/cx231xx-avcore.c

@@ -2133,7 +2133,7 @@ int cx231xx_tuner_post_channel_change(struct cx231xx *dev)
 
 	status = vid_blk_write_word(dev, DIF_AGC_IF_REF, dwval);
 
-	return status;
+	return status == sizeof(dwval) ? 0 : -EIO;
 }
 
 /******************************************************************************

drivers/media/usb/cx231xx/cx231xx-video.c

@@ -1322,6 +1322,7 @@ static int vidioc_g_tuner(struct file *file, void *priv, struct v4l2_tuner *t)
 	t->capability = V4L2_TUNER_CAP_NORM;
 	t->rangehigh = 0xffffffffUL;
 	t->signal = 0xffff;	/* LOCKED */
+	call_all(dev, tuner, g_tuner, t);
 
 	return 0;
 }
@@ -1350,6 +1351,9 @@ static int vidioc_g_frequency(struct file *file, void *priv,
 	struct cx231xx_fh *fh = priv;
 	struct cx231xx *dev = fh->dev;
 
+	if (f->tuner)
+		return -EINVAL;
+
 	f->type = fh->radio ? V4L2_TUNER_RADIO : V4L2_TUNER_ANALOG_TV;
 	f->frequency = dev->ctl_freq;