drm/amd/display: replace min/max nesting with clamp()

The clamp() macro explicitly expresses the intent of constraining
a value within bounds.Therefore, replacing min(max(a, b), c) with
clamp(val, lo, hi) can improve code readability.

Signed-off-by: Xichao Zhao <zhao.xichao@vivo.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>