gpu: host1x: Program interrupt destinations on Tegra234

On Tegra234, each Host1x VM has 8 interrupt lines. Each syncpoint
can be configured with which interrupt line should be used for
threshold interrupt, allowing for load balancing.

For now, to keep backwards compatibility, just set all syncpoints
to the first interrupt.

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