drm/amd/display: populate last calculated bb state with max clocks

[why]
update_bounding_box calculates intermediate bb states based on clock relationship
however, the last state doesn't need to maintain a minimum relationship, but should
actually contain maximum of every clock.  otherwise maximum clocks are not usable

[how]
once the calculated bb is built, override the last state with max values

Signed-off-by: Jun Lei <Jun.Lei@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>