drm/amd/powerplay: add ECC feature bit

It's OK to have this feature bit with old SMU firmwares.
But the feature should be disabled on them.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>