xtensa: remove legacy arch implementation

We re-wrote the xtensa arch code, but never got around
to purging the old implementation.

Removed those boards which hadn't been moved to the new
arch code. These were all xt-sim simulator targets and not
real hardware.

Fixes: #18138

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
67 files changed