drm/amdgpu: add the new common pm code to select the clock levels

This extends dpm clock level selection to the non-powerplay code paths.
This interface can be used to select individual clock levels.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Eric Huang <JinHuiEric.Huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>