[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>