s390/pci: do not modify function handles

Don't modify function handles to get a disabled handle - call
clp_disable_fh. With this change we also do no longer deconfigure
enabled functions.

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