mwifiex: limit channel number not to overflow memory

Limit the channel number in scan request, or the driver scan
config structure memory will be overflowed.

Cc: <stable@vger.kernel.org> # 3.5+
Signed-off-by: Stone Piao <piaoyun@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/mwifiex/cfg80211.c

@@ -1892,7 +1892,8 @@ mwifiex_cfg80211_scan(struct wiphy *wiphy,
 		}
 	}
 
-	for (i = 0; i < request->n_channels; i++) {
+	for (i = 0; i < min_t(u32, request->n_channels,
+			      MWIFIEX_USER_SCAN_CHAN_MAX); i++) {
 		chan = request->channels[i];
 		priv->user_scan_cfg->chan_list[i].chan_number = chan->hw_value;
 		priv->user_scan_cfg->chan_list[i].radio_type = chan->band;