drm/amd/powerplay: implment sysfs feature status function in smu

1. Unified feature enable status format in sysfs
2. Rename ppfeature to pp_features to adapt other pp sysfs node name
3. this function support all asic, not asic related function.

Signed-off-by: Kevin Wang <kevin1.wang@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Acked-by: Rui Huang <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>