drm/amd:Enable/Disable NBPSTATE on On/OFF of UVD

We observe black lines (underflow) on display when playing a
4K video with UVD. On Disabling Low memory P state this issue is
not seen.
In this patch ,disabling low memory P state only when video
size >= 4k.
Multiple runs of power measurement shows no impact

Signed-off-by: suresh guttula <suresh.guttula@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>