drm/amd/display: Reinstate LFC optimization

[why]
We want to streamline the calculations made when entering LFC.
Previously, the optimizations led to screen tearing and were backed out
to unblock development.

[how]
Integrate other calculations parameters, as well as screen tearing,
fixes with the original LFC calculation optimizations.

Signed-off-by: Amanda Liu <amanda.liu@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>