drm/amd/pm: implement the processor clocks which read by metric

The core processor clocks will be stored in smu metric table, then we
add this runtime information into amdgpu_pm_info interface.

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