s390/ap_bus: Make modules parameters visible in sysfs

Change the visibility of the module parameters ap_domain_index and
ap_thread_flag for the owner and the members of the owners group in
sysfs.

Previously the parameters where invisible due to a value of zero
as permissions parameter in the module_param_named macro.

Signed-off-by: Michael Veigel <veigel@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>