drm/amdgpu/discovery: enable ih v6 for OSS 6.0.1

Enable ih (interrupt handler) v6 for OSS 6.0.1.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Aaron Liu <aaron.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>