drm/amd/display: call pplib to update clocks

Allow pplib to update fclk and dcfclk for different voltage levels.
PPlib's values for dispclk and phyclk is not correct, so we are not
getting it from them. fclk is currently not used correctly, although
does not effect the actual fclk we request.

Signed-off-by: Eric Yang <Eric.Yang2@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>