staging: wfx: fix value of scan timeout

Before to start the scan request, the firmware signals (with a null
frame) to the AP it won't be able to receive data. This frame can be
long to send: up to 512TU. The current calculus of the scan timeout does
not take into account this delay.
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200515083325.378539-5-Jerome.Pouiller@silabs.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wfx/hif_tx.c

@@ -288,7 +288,7 @@ int hif_scan(struct wfx_vif *wvif, struct cfg80211_scan_request *req,
 	tmo_chan_bg = le32_to_cpu(body->max_channel_time) * USEC_PER_TU;
 	tmo_chan_fg = 512 * USEC_PER_TU + body->probe_delay;
 	tmo_chan_fg *= body->num_of_probe_requests;
-	tmo = chan_num * max(tmo_chan_bg, tmo_chan_fg);
+	tmo = chan_num * max(tmo_chan_bg, tmo_chan_fg) + 512 * USEC_PER_TU;
 
 	wfx_fill_header(hif, wvif->id, HIF_REQ_ID_START_SCAN, buf_len);
 	ret = wfx_cmd_send(wvif->wdev, hif, NULL, 0, false);