test/kms_plane_cursor: Honour max cursor size

Skip the tests for cursor sizes that are not supported by the hardware

Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>