[media] e4000: make VIDEO_V4L2 dependency optional

That tuner driver is mainly for DVB API, but there is some V4L2 API
controls for SDR usage. Make driver compile conditional so that V4L2
is not mandatory. Without the V4L2 support driver is build as a DVB
only, without SDR controls.

Fixes following errors reported by kbuild test robot:
ERROR: "v4l2_ctrl_auto_cluster" [drivers/media/tuners/e4000.ko] undefined!
ERROR: "v4l2_ctrl_new_std" [drivers/media/tuners/e4000.ko] undefined!
ERROR: "v4l2_ctrl_handler_init_class" [drivers/media/tuners/e4000.ko] undefined!
ERROR: "v4l2_ctrl_handler_free" [drivers/media/tuners/e4000.ko] undefined!

Reported-by: kbuild test robot <[e-mail]>
Cc: Hans Verkuil <[e-mail]>
Signed-off-by: Antti Palosaari <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/tuners/Kconfig

···
 
 config MEDIA_TUNER_E4000
 	tristate "Elonics E4000 silicon tuner"
-	depends on MEDIA_SUPPORT && I2C && VIDEO_V4L2
+	depends on MEDIA_SUPPORT && I2C
 	select REGMAP_I2C
 	default m if !MEDIA_SUBDRV_AUTOSELECT
 	help

drivers/media/tuners/e4000.c

···
 	return 0;
 }
 
+#if IS_ENABLED(CONFIG_VIDEO_V4L2)
 static int e4000_set_lna_gain(struct dvb_frontend *fe)
 {
 	struct e4000 *s = fe->tuner_priv;
···
 	.g_volatile_ctrl = e4000_g_volatile_ctrl,
 	.s_ctrl = e4000_s_ctrl,
 };
+#endif
 
 static const struct dvb_tuner_ops e4000_tuner_ops = {
 	.info = {
···
 	if (ret)
 		goto err;
 
+#if IS_ENABLED(CONFIG_VIDEO_V4L2)
 	/* Register controls */
 	v4l2_ctrl_handler_init(&s->hdl, 9);
 	s->bandwidth_auto = v4l2_ctrl_new_std(&s->hdl, &e4000_ctrl_ops,
···
 	}
 
 	s->sd.ctrl_handler = &s->hdl;
+#endif
 
 	dev_info(&s->client->dev,
 			"%s: Elonics E4000 successfully identified\n",
···
 
 	dev_dbg(&client->dev, "%s:\n", __func__);
 
+#if IS_ENABLED(CONFIG_VIDEO_V4L2)
 	v4l2_ctrl_handler_free(&s->hdl);
+#endif
 	memset(&fe->ops.tuner_ops, 0, sizeof(struct dvb_tuner_ops));
 	fe->tuner_priv = NULL;
 	kfree(s);