nouveau/gsp: document some aspects of GSP-RM

Document a few aspects of communication with GSP-RM. These comments are
derived from notes made during early development of GSP-RM support in
Nouveau, but were not included in the initial patch set.

Reviewed-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Timur Tabi <ttabi@nvidia.com>
Reviewed-by: Danilo Krummrich <dakr@redhat.com>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231122202840.2565153-1-ttabi@nvidia.com

nouveau/gsp: move to 535.113.01

This moves the initial effort to the latest 535 firmware.

The gsp msg structs have changed, and the message passing also.
The wpr also seems to have some struct changes.

This version of the firmware will be what we are stuck on for a while,
until we can refactor the driver and work out a better path forward.

Reviewed-by: Danilo Krummrich <dakr@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>