drm/amd/display: Updating Video Format Fall Back Policy.

[WHY]
Adding 1920x1080 as fail safe mode for
Video Format Fall Back Policy.

Reviewed-by: Jerry Zuo <Jerry.Zuo@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Jasdeep Dhillon <jdhillon@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>