[SCSI] qla2xxx: Correct list-iteration bug in Report-ID Acquisition codes.

Code in qla24xx_report_id_acquisition() incorrectly assumed that
upon completion of list iteration (with no match), the 'pos'
(vp) variable passed to list_for_each_entry() would be set to
NULL.  In this context, if the firmware were to return an
unrecognized vp_idx, the follow-on assignments to vp-members
could result in corruption of the structure.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: Saurav Kashyap <saurav.kashyap@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>