configs/xtrs: Removed the XTRS configuration This was an unverified port of...

configs/xtrs:  Removed the XTRS configuration This was an unverified port of NuttX to a TRS-80 simulator.  It was removed because (1) it is, as I said, unverified as well as unsupported, and (2) the TRS-80 simulation is a sub-optimal platform.  That platform includes a 16-bit ROM image and only a 48Kb RAM space.