drm/amdgpu: Don't print error on aux transaction timeouts

Since it's normal for DRM to retry our aux transaction helpers multiple
times in a row, up to 32 times for each attempted transaction, we're
making a lot of noise that is no longer necessary now that DRM will just
print the return code we give it.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Lyude <cpaul@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>