drm/tegra: vic: Implement explicit reset support

Tegra supports generic PM domains on 64-bit ARM, and if that is enabled,
the power domain code will make sure that resets are asserted and
deasserted at appropriate points in time.

If generic PM domains are not implemented, such as on 32-bit Tegra, the
resets need to be asserted and deasserted explicitly by the driver.

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