soc: xtensa: keep the CAVS old flasher still works

Keep the cavstwist.sh it is still working by specifying an
environment variable when CAVS_OLD_FLASHER is set. Provide
a fallback once the client-server-based tool does not work
well in some conditions.

Signed-off-by: Enjia Mai <enjia.mai@intel.com>
5 files changed