drm/amd/powerplay: add interface to get clock by type with voltage for display

This patch adds inteface to get clock by type with voltage, display will use it
to get current clocks with voltage.

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