[S390] cio: Disable channel measurements (cmf) on shutdown/reboot.

Disable channel measurements for all ccw devices via the ccw bus's
shutdown method. Clear residual cmf related information that may be
in the schib when setting up a new subchannel.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>