drm/amd/display: Array offset used before range check

Consolidating multiple CodeQL Fixes for alerts with rule id: cpp/offset-use-before-range-check

Reviewed-by: Joshua Aberback <joshua.aberback@amd.com>
Signed-off-by: Clay King <clayking@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>