[SCSI] zfcp: Remove some sparse warnings

Remove some sparse warnings by telling sparse that zfcp_req_create
acquires the lock for the request queue.

Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: Martin Peschke <mp3@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>