target/xtensa: import core lx106

target/xtensa: import core lx106

This is the core used in e.g. ESP8266 chips. Importing them
using import_core.sh, with the required files sourced from

https://github.com/espressif/xtensa-overlays

core-lx106.c was generated by the script; the only change is removing
the reference to core-matmap.h which doesn't seem to be available.

Signed-off-by: Simon Safar <simon@simonsafar.com>
Reviewed-by: Max Filippov <jcmvbkbc@gmail.com>
Message-Id: <20220423040835.29254-1-simon@simonsafar.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>