memory: tegra: Remove GPU from DRM IOMMU group

Commit 63a613fd ("memory: tegra: Add gr2d and gr3d to DRM IOMMU
group") added the GPU to the DRM IOMMU group, which doesn't make any
sense. This causes problems when Nouveau tries to attach to the SMMU
and causes it to fall back to using the DMA API.

Remove the GPU from the DRM groups to restore the old behaviour. The
GPU should always have its own IOMMU domain to make sure it can map
buffers into contiguous chunks (for big page support) without getting
in the way of mappings from the DRM group.

Cc: <stable@vger.kernel.org>
Fixes: 63a613fd ("memory: tegra: Add gr2d and gr3d to DRM IOMMU group")
Reported-by: Matias Zuniga <matias.nicolas.zc@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20200901153248.1831263-1-thierry.reding@gmail.comSigned-off-by: Krzysztof Kozlowski <krzk@kernel.org>

drivers/memory/tegra/tegra124.c

@@ -957,7 +957,6 @@ static const struct tegra_smmu_swgroup tegra124_swgroups[] = {
 static const unsigned int tegra124_group_drm[] = {
 	TEGRA_SWGROUP_DC,
 	TEGRA_SWGROUP_DCB,
-	TEGRA_SWGROUP_GPU,
 	TEGRA_SWGROUP_VIC,
 };