drm/amd/display: Update DTBCLK for DCN32

drm/amd/display: Update DTBCLK for DCN32

[Why&How]
- Implement interface to program DTBCLK DTO’s
  according to reference DTBCLK returned by PMFW
- This is required because DTO programming
  requires exact DTBCLK reference freq or it could
  result in underflow

Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>