Staging: rtl8192su: Correct use of ! and &

Correct priority problem in the use of ! and &.

The semantic patch that makes this change is as follows:
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@ expression E; constant C; @@
- !E & C
+ !(E & C)
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/rtl8192su/ieee80211/ieee80211_wx.c

@@ -843,7 +843,7 @@ int ieee80211_wx_get_encode_ext(struct ieee80211_device *ieee,
 	} else
 		idx = ieee->tx_keyidx;
 
-	if (!ext->ext_flags & IW_ENCODE_EXT_GROUP_KEY &&
+	if (!(ext->ext_flags & IW_ENCODE_EXT_GROUP_KEY) &&
 	    ext->alg != IW_ENCODE_ALG_WEP)
 		if (idx != 0 || ieee->iw_mode != IW_MODE_INFRA)
 			return -EINVAL;