[PATCH] xtensa: fix memory corruption by broken sysregs

[Nick Clifton]

Hi Max,

> bfd/
> 2017-08-02  Max Filippov  <jcmvbkbc@gmail.com>
> 
> 	* xtensa-isa.c (xtensa_isa_init): Don't update lookup table
> 	entries for sysregs with negative indices.

Approved and applied.

Cheers
  Nick