drm/amd/display: Extend dmub_cmd_psr_copy_settings_data struct

Reserve padding bytes for new feature implementation

Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Ian Chen <ian.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>