drm/amd/display: replace clocks_value struct with dc_clocks

This will avoid structs with duplicate information. Also
removes pixel clock voltage request. This has no effect since
pixel clock does not affect dcn voltage and this function only
matters for dcn.

Signed-off-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@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>