drm/amdgpu: Default disable GDS for compute+gfx

Units in the GDS block default to allowing all VMIDs access to all
entries. Disable shader access to the GDS, GWS, and OA blocks from all
compute and gfx VMIDs by default. For compute, HWS firmware will set
up the access bits for the appropriate VMID when a compute queue
requires access to these blocks.
The driver will handle enabling access on-demand for graphics VMIDs.

Leaving VMID0 with full access because otherwise HWS cannot save or
restore values during task switch.

v2: Fixed code and comment styling.

Signed-off-by: Joseph Greathouse <Joseph.Greathouse@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>