drm/amd/display: Allow Latency Increase For Last Strategy

[Why]
Playing 1080p video on 4k60 timing uses UCLK DPM5 and mode support
determines that p-state switching is not supported.

[How]
Allow DML to increase latency as the last strategy so strategies such
as VBlank p-state switching may become possible

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Signed-off-by: Austin Zheng <Austin.Zheng@amd.com>
Signed-off-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>