Fix point rendering.

Change-Id: I8262fa4bc527d719680d83bf9a1b8e88bdae07f8
Reviewed-on: https://swiftshader-review.googlesource.com/3514
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>