rtlwifi: rtl8723ae: Make rtl8723e_dm_refresh_rate_adaptive_mask static

Fix sparse warning:

drivers/net/wireless/realtek/rtlwifi/rtl8723ae/dm.c:666:6:
 warning: symbol 'rtl8723e_dm_refresh_rate_adaptive_mask' was not declared. Should it be static?
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/realtek/rtlwifi/rtl8723ae/dm.c

@@ -663,7 +663,7 @@ void rtl8723e_dm_init_rate_adaptive_mask(struct ieee80211_hw *hw)
 
 }
 
-void rtl8723e_dm_refresh_rate_adaptive_mask(struct ieee80211_hw *hw)
+static void rtl8723e_dm_refresh_rate_adaptive_mask(struct ieee80211_hw *hw)
 {
 	struct rtl_priv *rtlpriv = rtl_priv(hw);
 	struct rtl_hal *rtlhal = rtl_hal(rtl_priv(hw));