drm/i915/guc: Remove some obsolete definitions

There were a bunch of defines and structures left over from an API
update a very long time ago. Remove them.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230531155942.441862-1-John.C.Harrison@Intel.com