drm/amd/display: Update SW cursor fallback for subvp high refresh

[Description]
Since SubVP high refresh is now enabled, we must
fallback to SW cursor under if we're in a SubVP
high refresh config

Reviewed-by: Samson Tam <samson.tam@amd.com>
Acked-by: Alan Liu <haoping.liu@amd.com>
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>