drm/amdgpu/gmc11: disable AGP on GC 11.5

AGP aperture is deprecated and no longer functional.

v2: fix typo (Alex)
v3: just skip the agp setup call
v4: revert back to the original model
v5: back to v3

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

drivers/gpu/drm/amd/amdgpu/gmc_v11_0.c

@@ -635,7 +635,8 @@ static void gmc_v11_0_vram_gtt_location(struct amdgpu_device *adev,
 
 	amdgpu_gmc_vram_location(adev, &adev->gmc, base);
 	amdgpu_gmc_gart_location(adev, mc);
-	if (!amdgpu_sriov_vf(adev))
+	if (!amdgpu_sriov_vf(adev) ||
+	    (amdgpu_ip_version(adev, GC_HWIP, 0) < IP_VERSION(11, 5, 0)))
 		amdgpu_gmc_agp_location(adev, mc);
 
 	/* base offset of vram pages */