qcacmn: Add support to append scan channel list

Add append bit in scan channel list command. If append bit
is set, new channels will be appended to existing channel
list else existing channel list will be over written
by new channel list.

Change-Id: I0b1ecd2b809aafe6e524a05aacd5b14c80640556
CRs-Fixed: 2159802

wmi_unified_tlv.c

@@ -2701,6 +2701,9 @@ static QDF_STATUS send_scan_chan_list_cmd_tlv(wmi_unified_t wmi_handle,
 
 	WMI_LOGD("no of channels = %d, len = %d", chan_list->nallchans, len);
 
+	if (chan_list->append)
+		cmd->flags |= APPEND_TO_EXISTING_CHAN_LIST;
+
 	cmd->pdev_id = wmi_handle->ops->convert_pdev_id_host_to_target(
 							chan_list->pdev_id);
 	cmd->num_scan_chans = chan_list->nallchans;