xf86-video-tseng: Mark broken and set epiry date

Mark xf86-video-tseng as broken, it doesn't build with xserver 1.20.7, and
there is no upstream patch available to fix it.
Set it to epire on May 1, that should give any users ample time to fix it,
and it will give people using quarterly branches a heads up as well.
Keep the BROKEN_arch lines as a reminder that it was broken on those arches
even before this.