staging: rtl8723bs: fix u8 less than zero check

The error variable ret is currently a u8 and so two comparisons
to see if an error return is less than zero will always be false
because ret is unsigned.  Fix this by making ret an int.

Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c

@@ -3255,7 +3255,7 @@ static int cfg80211_rtw_sched_scan_start(struct wiphy *wiphy,
 
 	struct adapter *padapter = (struct adapter *)rtw_netdev_priv(dev);
 	struct	mlme_priv *pmlmepriv = &(padapter->mlmepriv);
-	u8 ret;
+	int ret;
 
 	if (padapter->bup == false) {
 		DBG_871X("%s: net device is down.\n", __func__);