[media] media: em28xx - fix i2c_xfer to return -ENODEV when dev is removed

In em28xx usb disconnect code path, some dvb fe and tuner drivers
attempt i2c transfers from their release interfaces. When device
is removed, return -ENODEV instead of attempting to transfer data
over i2c.

Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/usb/em28xx/em28xx-i2c.c

@@ -501,6 +501,12 @@ static int em28xx_i2c_xfer(struct i2c_adapter *i2c_adap,
 	int addr, rc, i;
 	u8 reg;
 
+	/* prevent i2c xfer attempts after device is disconnected
+	   some fe's try to do i2c writes/reads from their release
+	   interfaces when called in disconnect path */
+	if (dev->disconnected)
+		return -ENODEV;
+
 	rc = rt_mutex_trylock(&dev->i2c_bus_lock);
 	if (rc < 0)
 		return rc;