drm/tegra: gr2d: Explicitly control module reset

As of commit 4782c0a5 ("clk: tegra: Don't deassert reset on enabling
clocks"), module resets are no longer automatically deasserted when the
module clock is enabled. To make sure that the gr2d module continues to
work, we need to explicitly control the module reset.

Fixes: 4782c0a5

 ("clk: tegra: Don't deassert reset on enabling clocks")
Signed-off-by: Thierry Reding <treding@nvidia.com>