staging: rtl8188eu: Fix incorrect response to SIOCGIWESSID

When not associated with an AP, wifi device drivers should respond to the
SIOCGIWESSID ioctl with a zero-length string for the SSID, which is the
behavior expected by dhcpcd.

Currently, this driver returns an error code (-1) from the ioctl call,
which causes dhcpcd to assume that the device is not a wireless interface
and therefore it fails to work correctly with it thereafter.

This problem was reported and tested at
https://github.com/lwfinger/rtl8188eu/issues/234.
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8188eu/os_dep/ioctl_linux.c

@@ -1395,19 +1395,13 @@ static int rtw_wx_get_essid(struct net_device *dev,
 	if ((check_fwstate(pmlmepriv, _FW_LINKED)) ||
 	    (check_fwstate(pmlmepriv, WIFI_ADHOC_MASTER_STATE))) {
 		len = pcur_bss->Ssid.SsidLength;
-
-		wrqu->essid.length = len;
-
 		memcpy(extra, pcur_bss->Ssid.Ssid, len);
-
-		wrqu->essid.flags = 1;
 	} else {
-		ret = -1;
-		goto exit;
+		len = 0;
+		*extra = 0;
 	}
-
-exit:
-
+	wrqu->essid.length = len;
+	wrqu->essid.flags = 1;
 
 	return ret;
 }