[media] em28xx: fix PCTV 290e LNA oops

Pointer to device state has been moved to different location during
some change. PCTV 290e LNA function still uses old pointer, carried
over FE priv, and it crash.
Reported-by: Janne Kujanpää <jikuja@iki.fi>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Cc: stable@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/usb/em28xx/em28xx-dvb.c

@@ -717,7 +717,8 @@ static void pctv_520e_init(struct em28xx *dev)
 static int em28xx_pctv_290e_set_lna(struct dvb_frontend *fe)
 {
 	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
-	struct em28xx *dev = fe->dvb->priv;
+	struct em28xx_i2c_bus *i2c_bus = fe->dvb->priv;
+	struct em28xx *dev = i2c_bus->dev;
 #ifdef CONFIG_GPIOLIB
 	struct em28xx_dvb *dvb = dev->dvb;
 	int ret;