drm/amd/display: Update cursor limits based on SW cursor fallback limits

[Why&How]
For determining the cursor size limit, use the same checks that
are used for determining SW cursor fallback instead of only
using SubVP

Reviewed-by: Aric Cyr <aric.cyr@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@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>