spdm: Fix session reset logic

Session reset should not reset the public key that is initialized when
creating the session, otherwise the key will be lost.

BUG=b:338528575
TEST=spdm unittests

Change-Id: Ib2ba3012abeaefce680007958865f530089caf21
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/spdm/+/5526572
Tested-by: Howard Yang <hcyang@google.com>
Commit-Queue: ChromeOS Auto Retry <chromeos-auto-retry@chromeos-bot.iam.gserviceaccount.com>
Reviewed-by: Vadim Sukhomlinov <sukhomlinov@google.com>
3 files changed