drm/amdgpu: disable gpu reset on Vangogh for now

Until the issues in the SMU firmware are fixed.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Huang Rui <ray.huang@amd.com>