gpu: host1x: Enable gather filter

The gather filter is a feature present on Tegra124 and newer where the
hardware prevents GATHERed command buffers from executing commands
normally reserved for the CDMA pushbuffer which is maintained by the
kernel driver.

This commit enables the gather filter on all supporting hardware.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>