drm/amdgpu: add TOC firmware support for apu (v3)

APU needs load toc firmware for gfx10 series on psp front door loading.

v2: rebase against latest code
v3: clarify error message

Signed-off-by: Huang Rui <ray.huang@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>