Fix string equality comparison

Don't use "==" to compare strings.

Bug: 25624963
Change-Id: Id25696e4fdcbcf4d48ec74e8ed65c1a33716b30c

wifi/java/android/net/wifi/WifiEnterpriseConfig.java

@@ -838,7 +838,7 @@ public class WifiEnterpriseConfig implements Parcelable {
         StringBuffer sb = new StringBuffer();
         for (String key : mFields.keySet()) {
             // Don't display password in toString().
-            String value = (key == PASSWORD_KEY) ? "<removed>" : mFields.get(key);
+            String value = PASSWORD_KEY.equals(key) ? "<removed>" : mFields.get(key);
             sb.append(key).append(" ").append(value).append("\n");
         }
         return sb.toString();