DMCU-B (Display Micro-Controller Unit B) is a display microcontroller
used for shared display functionality with BIOS and for advanced
power saving display features.

Extends the command header to include new DCN3.1 functionality.

Adds new interfaces to DC dmub interface as well for z-state support.
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>