staging: wlan-ng: fix exit return when sme->key_idx >= NUM_WEPKEYS

Currently the exit return path when sme->key_idx >= NUM_WEPKEYS is via
label 'exit' and this checks if result is non-zero, however result has
not been initialized and contains garbage.  Fix this by replacing the
goto with a return with the error code.

Addresses-Coverity: ("Uninitialized scalar variable")
Fixes: 0ca6d8e7 ("Staging: wlan-ng: replace switch-case statements with macro")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20191014110201.9874-1-colin.king@canonical.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wlan-ng/cfg80211.c

@@ -469,10 +469,8 @@ static int prism2_connect(struct wiphy *wiphy, struct net_device *dev,
 	/* Set the encryption - we only support wep */
 	if (is_wep) {
 		if (sme->key) {
-			if (sme->key_idx >= NUM_WEPKEYS) {
-				err = -EINVAL;
-				goto exit;
-			}
+			if (sme->key_idx >= NUM_WEPKEYS)
+				return -EINVAL;
 
 			result = prism2_domibset_uint32(wlandev,
 				DIDMIB_DOT11SMT_PRIVACYTABLE_WEPDEFAULTKEYID,