rtw88: Delete useless kfree code

The parameter of kfree function is NULL, so kfree code is useless, delete it.
Signed-off-by: NZheng Yongjun <zhengyongjun3@huawei.com>
Acked-by: NPing-Ke Shih <pkshih@realtek.com>
Signed-off-by: NKalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201216130442.13869-1-zhengyongjun3@huawei.com

drivers/net/wireless/realtek/rtw88/main.c

@@ -1276,7 +1276,6 @@ static void rtw_set_supported_band(struct ieee80211_hw *hw,
 
 err_out:
 	rtw_err(rtwdev, "failed to set supported band\n");
-	kfree(sband);
 }
 
 static void rtw_unset_supported_band(struct ieee80211_hw *hw,