[S390] cio: ccw group online store - report rcs to the caller.

In case the ccw group driver refuses to set a device [on|off]line,
we should transmit the return code to the caller.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>