drm/amd/powerplay: update smu11_driver_if_arcturus.h

It guides how driver should interface with SMU in arcturus.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>