cmake: fix WITH_VTK usage

'WITH_' variables is intended to enable CMake scripts with some autodetection logic.
'WITH_' can be off, but components is really enabled via command-line options
with proper variables setup (including 'HAVE_').

modules/viz/CMakeLists.txt

@@ -1,4 +1,4 @@
-if(NOT WITH_VTK OR NOT DEFINED HAVE_VTK OR NOT HAVE_VTK)
+if(NOT HAVE_VTK)
   ocv_module_disable(viz)
 endif()