drm/amdgpu/psp: keep TMR in visible vram region for SRIOV

Fix compute ring test failure in sriov scenario.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Tianci.Yin <tianci.yin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>