nl80211: Fix channel 14 use

nl80211 interface has a trivial bug that prevents it to work correctly
with channel 14. Channel frequency is erroneously 2848 instead of 2484.
To correct it just apply this patch. [Bug 308]

src/drivers/driver_nl80211.c

@@ -1720,7 +1720,7 @@ static int phy_info_handler(struct nl_msg *msg, void *arg)
 
 			/* crude heuristic */
 			if (mode->channels[idx].freq < 4000)
-				if (mode->channels[idx].freq == 2848)
+				if (mode->channels[idx].freq == 2484)
 					mode->channels[idx].chan = 14;
 				else
 					mode->channels[idx].chan = (mode->channels[idx].freq - 2407) / 5;