scsi: lpfc: fix missing spin_unlock on sql_list_lock

From: Colin Ian King <colin.king@canonical.com>

In the case where sglq is null, the current code just returns without
unlocking the spinlock sql_list_lock. Fix this by breaking out of the
while loop and the exit path will then unlock and return NULL as was
the original intention.

Detected by CoverityScan, CID#1411635 ("Missing unlock")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>