drm/amd/display: Add num_slices_h to set_dto_dscclk signature

Add the number of horizontal slices argument to allow configuring clock
based on slice number.

Reviewed-by: Nevenko Stupar <nevenko.stupar@amd.com>
Signed-off-by: Ilya Bakoulin <Ilya.Bakoulin@amd.com>
Signed-off-by: Fangzhi Zuo <jerry.zuo@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>