drm/amd/display: Split DMUB cmd type into type/subtype

[Why]
Commands will be considered a stable ABI between driver and firmware.

Commands are also split between DC commands, DAL feature commands,
and VBIOS commands.

Commands are currently not designated to a specific ID and the enum
does not provide a stable ABI.

We currently group all of these into a single command type of 8-bits.
With the stable ABI consideration in mind it's not unreasonable to
run out of command IDs.

For cleaner separation and versioning split the commands into a main
type and a subtype.

[How]
For commands where performance matters (like reg sequences) these
are still considered main commands.

Sub commands will be split by ownership/feature.

Update existing command sequences to reflect new changes.

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>