drm/amdgpu: set mode1 reset as default for dimgrey_cavefish

Use mode1 reset for dimgrey_cavefish by default.

Signed-off-by: Tao Zhou <tao.zhou1@amd.com>
Reviewed-by: Jiansong Chen <Jiansong.Chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>