s390/cio: don't register chpids in reserved state

During IPL we register all chpids that are not in the unrecognized
state. This includes chpids that are not usable and chpids for which
the state could not be obtained.

Change that to only register chpids in the configured (usable) or
standby (usable after a configure operation) state. All other chpids
could only be made available by external control for which we would
receive machine checks.

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