drm/amdgpu: Skip the VRAM base offset on SRIOV

[Why]
As VF cannot read MMMC_VM_FB_OFFSET with L1 Policy(read 0xffffffff).
It leads to driver get the incorrect vram base offset.

[How]
Since SR-IOV is dGPU only, skip reading this register and set the
fb_offest to 0.
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Yifan Zha <Yifan.Zha@amd.com>
Signed-off-by: Horace Chen <horace.chen@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -649,6 +649,9 @@ static void gmc_v11_0_vram_gtt_location(struct amdgpu_device *adev,
 	amdgpu_gmc_gart_location(adev, mc);
 
 	/* base offset of vram pages */
+	if (amdgpu_sriov_vf(adev))
+		adev->vm_manager.vram_base_offset = 0;
+	else
 		adev->vm_manager.vram_base_offset = adev->mmhub.funcs->get_mc_fb_offset(adev);
 }