drm/amd/display: Rearrange dmub_cmd defs order

 - Rearranged defs order

Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Anthony Koo <anthony.koo@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>