drm/amd/display: Clip all remaining regamma points after first clipped point

[Why]
All values computed in the gamma curve after the first upperbound
clipped point will need to be clipped anyways. We can avoid
unnecessary computations and potential fixed point
overflow by instead clipping these values to 1 automatically.

[How]
Track if upper-bound clipping has been done, and clip all values after
this threshold is reached without computing the output gamma
point.

Signed-off-by: SivapiriyanKumarasamy <sivapiriyan.kumarasamy@amd.com>
Reviewed-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>