drm/amd/display: Disable dpstreamclk, symclk32_se, and symclk32_le

[Why & How]
Disable dpstreamclk, symclk32_se, and symclk32_le when not in use.

Reviewed-by: Ariel Bernstein <eric.yang2@amd.com>
Acked-by: Agustin Gutierrez Sanchez <agustin.gutierrez@amd.com>
Signed-off-by: Jake Wang <haonan.wang2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>