[SCSI] zfcp: Update message and add description

Update the newly introduced message for the boxed status to conform to
match the style of s390 and zfcp messages.

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@HansenPartnership.com>