drm/amdgpu: Use optimal mtypes and PTE bits for Arcturus

For compute VRAM allocations on Arturus use the new RW mtype
for non-coherent local memory, CC mtype for coherent local
memory and PTE_SNOOPED bit for invalidating non-dirty cache
lines on remote XGMI mappings.

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Tested-by: Amber Lin <Amber.Lin@amd.com>
Reviewed-by: Shaoyun Liu <Shaoyun.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>