Avoids spurious port errors when plugging and unplugging devices on
the DM250.

Just note the change and notify the root hub. Fixes a hard lockup
on the DM250 when unplugging an OTG hub.

Disestablish interrupt on detach

On resume we'll already have root mounted so we can't use
config_mountroot or it will lock against it self since
config_mountroot doesn't defer to a thread.