drm/amdgpu: Skip TMR allocation if not required

On ASICs with PSPv13.0.6, TMR is reserved at boot time. There is no need
to allocate TMR region by driver. However, it's still required to send
SETUP_TMR command to PSP.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>