drm/amd/display: Call hwss.set_cursor_sdr_white_level, if available

[Why]
In HDR configurations, the cursor - in SDR - needs to have it's white
level boosted.

[How]
Program the cursor boost in update_dchubp_dpp like the other cursor
attributes.

Signed-off-by: SivapiriyanKumarasamy <sivapiriyan.kumarasamy@amd.com>
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Acked-by: Reza Amini <Reza.Amini@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>