From: Martin Schwidefsky <schwidefsky@de.ibm.com>

DASD driver fixes:
 - Fix generic_set_online if diag discipline is not availab.e
 - Fix reserve on already reserved device.
 - Use default-erp for unit check without sence information.
 - Revert dasd naming scheme change from dasd<xyz> to dasd_<busid>_. This
   breaks too many user space packages.
 - Extend dasd naming scheme to four letters dasd<aaaa>-dasd<zzzz>.
 - Fix formatting of dasds.