qeth: Remove usage of subsys.rwsem

the current driver tree contains the removal of subsys.rwsem.
Unfortunately, this breaks qeth. However, it should be no problem to
fix the walking of the devices for /proc/qeth:

No need to take subsys.rwsem during walking the devices,
driver_find_devices() should already suffice.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>