drm/amd/display: add support for DTO genarated dscclk

Current implementation will choose to use refclk as dscclk. This is not
recommended by hardware team as refclk is a fixed value which could
cause unnecessary power consumption or it could be not enough for large
DSC timings. So we are adding new interfaces so we could switch to use
dynamically generated DSCCLK by DTO. So DSCCLK is programmable based on
current pixel clock and dispclk.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Chaitanya Dhere <chaitanya.dhere@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>