avoid clutter in erp_dbf

cleanup zfcp_fsf_req_dismiss functions:
- avoid clutter in erp_dbf (reqs_active is always 0)
- fold called three-line function into calling function
- add meaningful comment
- coding style
Signed-off-by: NMartin Peschke <mp3@de.ibm.com>
Signed-off-by: NSwen Schillig <swen@vnet.ibm.com>
Signed-off-by: NJames Bottomley <James.Bottomley@SteelEye.com>