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.h b/drivers/net/wireless/wl12xx/wl1251.h
index 4f5f02a..6b942a2 100644
--- a/drivers/net/wireless/wl12xx/wl1251.h
+++ b/drivers/net/wireless/wl12xx/wl1251.h
@@ -381,6 +381,9 @@
 
 	u32 chip_id;
 	char fw_ver[21];
+
+	/* Most recently reported noise in dBm */
+	s8 noise;
 };
 
 int wl1251_plt_start(struct wl1251 *wl);