Improve ENA reset handling

For easier debugging, the reset is being triggered and the reset reason is
being set only in case it is done for the first time. Such approach will
ensure that the first reset reason is not going to be overwritten and
will make it easier for debugging.

Also, add a reset trigger upon invalid Tx requested ID.

Submitted by: Michal Krawczyk <mk@semihalf.com>
Obtained from: Semihalf
Sponsored by: Amazon, Inc.