staging: rtl8192e: rtl_wx: fix negative noise value

wstats->qual.noise is of type uint8, so it shouldn't be assigned a
negative number. Assigning it 0x100 - 100, which is the equivalent
to -100 dBm when IW_QUAL_DBM is set.
Signed-off-by: Luis de Bethencourt <luisbg@osg.samsung.com>
Tested-by: Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192e/rtl8192e/rtl_wx.c

@@ -1225,7 +1225,7 @@ static struct iw_statistics *_rtl92e_get_wireless_stats(struct net_device *dev)
 	if (ieee->state < RTLLIB_LINKED) {
 		wstats->qual.qual = 10;
 		wstats->qual.level = 0;
-		wstats->qual.noise = -100;
+		wstats->qual.noise = 0x100 - 100;	/* -100 dBm */
 		wstats->qual.updated = IW_QUAL_ALL_UPDATED | IW_QUAL_DBM;
 		return wstats;
 	}