drm/amdgpu: drop some kernel messages in VCN code

We have messages when the VCN fails to initialize and
there is no need to report on success.
Also PSP loading FWs is the default for production.

Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Sonny Jiang <sonjiang@amd.com>
Signed-off-by: David (Ming Qiang) Wu <David.Wu3@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>