wireless: fix premature removal of hotplug devices due to down state

wireless: fix premature removal of hotplug devices due to down state

When a device is added that isn't up, status toggles can sometimes lead to a
DEV_EVENT_REMOVE event, which causes the device to be removed from an interface
or a bridge.
Fix this by toggling the dev->disabled status instead based on IFF_UP, and
adding a check to bridge/interface code to only permanently remove devices that
are actually gone.

Fixes: 516ab774cc16 ("system-linux: fix race condition on bringing up wireless devices")
Signed-off-by: Felix Fietkau <nbd@nbd.name>