[SCSI] zfcp: Enable debug feature before setting adapter online

Already register the debug feature before the zfcp adapter is
set online. This allows to use the debug feature to investigate
the online/offline sequence.

Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: Swen Schillig <swen@vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>