drm/amdgpu: Add API to get tmr info from acpi

In certain configs, TMR information is available from ACPI. Add API to
fetch the information.

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>