gpu: host1x: Fix Tegra194 syncpt interrupt threshold

Syncpoint interrupts are not working as expected on Tegra194. The
problem is that the syncpoint interrupt threshold being used is the
global interrupt threshold and not the virtual interrupt threshold.
Fix this by using the virtual interrupt threshold which aligns with
downstream.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>