[media] cx231xx: fix device disconnect checks

The driver were using DEV_MISCONFIGURED on some places, and
DEV_DISCONNECTED on others. In a matter of fact, DEV_MISCONFIGURED
were set only during the usb disconnect callback, with
was confusing.

Also, the alsa driver never checks if the device is present,
before doing some dangerous things.

Remove DEV_MISCONFIGURED, replacing it by DEV_DISCONNECTED.

Also, fixes the other usecases for DEV_DISCONNECTED.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>