gpu: nova-core: do not import firmware commands into GSP command module

gpu: nova-core: do not import firmware commands into GSP command module

Importing all the firmware commands like we did is a bit confusing, as
the layer of a command type (fw or GSP) cannot be inferred from looking
at its name alone. Furthermore it makes it impossible to create commands
that have the same name as their firmware command.

Thus, stop importing all commands and refer to them from the `fw` module
instead.

Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>
Link: https://patch.msgid.link/20260521-nova-unload-v6-2-65f581c812c9@nvidia.com
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>