[SCSI] zfcp: Fix check whether unchained ct_els is possible

A false check was performed whether an unchained ct_els
is possible or not.

Signed-off-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>