drm/amd/display: fix buffer overruns warnings

drm/amd/display: fix buffer overruns warnings

[Why & How]
Fixes a warning by adding bounds checks and index validation in dml2_0
sources to address static analysis warnings. Ensures safe array access and
prevents out-of-bounds reads by validating indices before use, improving
robustness and reliability in the affected files.

Reviewed-by: Austin Zheng <austin.zheng@amd.com>
Signed-off-by: Gaghik Khachatrian <gaghik.khachatrian@amd.com>
Signed-off-by: James Lin <pinglei.lin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>