drm/amd/display: Add missing DP_SEC register definitions and masks

[Why]
some DP_SEC register defs and masks are missing.

[How]
add the missing defs and masks.

Signed-off-by: Max Tseng <chuan-yu.tseng@amd.com>
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>