drm/amd/dc: Use atombios api directly in DC

In order to remove the cgs wrapper functions for atombios api.

Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>