wl1251: add get_survey callback in order to get channel noise

Signed-off-by: John W. Linville <linville@tuxdriver.com>
Acked-by: Kalle Valo <kvalo@adurom.com>
diff --git a/drivers/net/wireless/wl12xx/wl1251_rx.c b/drivers/net/wireless/wl12xx/wl1251_rx.c
index 8515158..1b6294b 100644
--- a/drivers/net/wireless/wl12xx/wl1251_rx.c
+++ b/drivers/net/wireless/wl12xx/wl1251_rx.c
@@ -74,6 +74,12 @@
 
 	status->signal = desc->rssi;
 
+	/*
+	 * FIXME: guessing that snr needs to be divided by two, otherwise
+	 * the values don't make any sense
+	 */
+	wl->noise = desc->rssi - desc->snr / 2;
+
 	status->freq = ieee80211_channel_to_frequency(desc->channel);
 
 	status->flag |= RX_FLAG_TSFT;