qcacmn: Fix OOB issue for bwnss oui

If is_bwnss_oui return true in util_scan_parse_vendor_ie,
and it will run into below logical:
scan_params->ie_list.bwnss_map = (((uint8_t *)ie) + 8)
But in fact if ie->ie_len < 6, it will casue read out
of boundary issue. So add the length chekcing before
reading it

Change-Id: I0cdf723154eb808f8062efd897f9d67d54d4573b
CRs-Fixed: 2838849