drm/amdgpu: extend PSP GFX FW type

Extend PSP GFX FW type to support IMU, LSDMA, SDMA v6, RS64 MES related
fw load.

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>