Fix warning about unhandled enumeration values in tst_sqldriver.

Change-Id: I4e750982aab861abbbbabe980a663f8b118cdf54
Reviewed-by: Laszlo Papp <lpapp@kde.org>
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>

tests/auto/sql/kernel/qsqlresult/testsqldriver.h

@@ -81,6 +81,8 @@ public:
         case QSqlDriver::PreparedQueries:
         case QSqlDriver::NamedPlaceholders:
             return true;
+        default:
+            break;
         }
         return false;
     }