Fix up vao usage in qquickviewcomparison example

The binder calls create() if needed, so drop that call.
In the render function however, drop the binder.
Trying to create() again and again on every frame is a
waste of time.

Change-Id: I1e9cd8e2c97030b96e604256661e65ce75446e9d
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>