mei: Remove all bus devices from the mei_dev list when stopping the MEI

When stopping the MEI, we should remove and potentially unregister
all bus devices queued on the mei_dev linked list.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>