[SCSI] zfcp: Return -ENOMEM for allocation failures in zfcp_fsf

When a fsf_req or a qtcb cannot be allocated return -ENOMEM instead of
-EIO.

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>