drm/amdgpu: query sram ecc/ecc availability from atombios

query sram ecc capability via amdgpu_atomfirmware_ecc_default_enabled
query ecc availability via amdgpu_atomfirmware_sram_ecc_supported

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