gpu: host1x: Don't skip assigning syncpoints to channels

The code to write the syncpoint channel assignment register
incorrectly skips the write if hypervisor registers are not available.

The register, however, is within the guest aperture so remove the
check and assign syncpoints properly even on virtualized systems.

Fixes: c3f52220 ("gpu: host1x: Enable Tegra186 syncpoint protection")
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>