[SCSI] zfcp: Only collect FSF/HBA debug data for matching trace levels

The default trace level is to only trace failed FSF commands. Thus it
is not necessary to collect trace data for most FSF commands, since
it will be thrown away later. Restructure the FSF/HBA trace
infrastructure to first check the trace level in a inline function and
only do the expensive data collection for matching trace levels.

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