staging: rtl8192u: make in ieee80211/ieee80211_wx.c a local variable static

Make some local variable eee80211_modes static.

Fix sparse warnings:
drivers/staging/rtl8192u/ieee80211/ieee80211_wx.c:42:19: warning: symbol 'ieee80211_modes' was not declared. Should it be static?
Signed-off-by: Ana Rey <anarey@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/ieee80211/ieee80211_wx.c

@@ -39,7 +39,7 @@ struct modes_unit {
 	char *mode_string;
 	int mode_size;
 };
-struct modes_unit ieee80211_modes[] = {
+static struct modes_unit ieee80211_modes[] = {
 	{"a",1},
 	{"b",1},
 	{"g",1},