[S390] cio: Allow 0 and 1 as input for channel path status attribute.

Channel path status can now be modified by writing '0' and '1'
to the sysfs status attribute in addition to 'offline' and
'online' respectively.

Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>