rtlwifi: Fix warnings on parisc arch

In "Build regressions/improvements in v3.0-rc2", Geert Uytterhoeven
reports a number of warnings that occur for parisc builds of rtlwifi
and dependents.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rtlwifi/wifi.h b/drivers/net/wireless/rtlwifi/wifi.h
index 9d003e0..fcf2c9f 100644
--- a/drivers/net/wireless/rtlwifi/wifi.h
+++ b/drivers/net/wireless/rtlwifi/wifi.h
@@ -1983,7 +1983,7 @@
 
 static inline struct ieee80211_sta *get_sta(struct ieee80211_hw *hw,
 					    struct ieee80211_vif *vif,
-					    u8 *bssid)
+					    const u8 *bssid)
 {
 	return ieee80211_find_sta(vif, bssid);
 }