staging: rtl8192e: remove bogus ssid character sign test

This error triggers on some architectures with unsigned `char` types:

drivers/staging/rtl8192e/rtllib_softmac_wx.c:459 rtllib_wx_set_essid() warn: impossible condition '(extra[i] < 0) => (0-255 < 0)'

But actually, the entire test is bogus, as ssids don't have any sign
validity rules like that. So just remove this check look all together.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-staging@lists.linux.dev
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20221025122150.583617-1-Jason@zx2c4.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: zx2c4

drivers/staging/rtl8192e/rtllib_softmac_wx.c

@@ -439,7 +439,7 @@ int rtllib_wx_set_essid(struct rtllib_device *ieee,
 			union iwreq_data *wrqu, char *extra)
 {
 
-	int ret = 0, len, i;
+	int ret = 0, len;
 	short proto_started;
 	unsigned long flags;
 
@@ -455,13 +455,6 @@ int rtllib_wx_set_essid(struct rtllib_device *ieee,
 		goto out;
 	}
 
-	for (i = 0; i < len; i++) {
-		if (extra[i] < 0) {
-			ret = -1;
-			goto out;
-		}
-	}
-
 	if (proto_started)
 		rtllib_stop_protocol(ieee, true);