scsi: qla2xxx: Fix serialization of DCBX TLV data request

Commit b6faaaf7 ("scsi: qla2xxx: Serialize mailbox request") serialized
mailbox requests from userspace using the 'optrom' mutex. However, in the
case of DCBX TLV data, if the memory for it is already allocated, then the
mailbox request ends up not being serialized because it is done without
holding the 'optrom' mutex.

Link: https://lore.kernel.org/r/20220926230245.790508-1-rafaelmendsr@gmail.com
Fixes: b6faaaf7 ("scsi: qla2xxx: Serialize mailbox request")
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qla2xxx/qla_attr.c

@@ -951,9 +951,9 @@ qla2x00_sysfs_read_dcbx_tlv(struct file *filp, struct kobject *kobj,
 	if (!capable(CAP_SYS_ADMIN) || off != 0 || count > DCBX_TLV_DATA_SIZE)
 		return 0;
 
+	mutex_lock(&vha->hw->optrom_mutex);
 	if (ha->dcbx_tlv)
 		goto do_read;
-	mutex_lock(&vha->hw->optrom_mutex);
 	if (qla2x00_chip_is_down(vha)) {
 		mutex_unlock(&vha->hw->optrom_mutex);
 		return 0;