spdm: Implement data phase encryption

The data phase uses different key (the main secret) for
encryption/decryption. Implement those functionalities.

BUG=b:284394614
TEST=spdm unittests

Change-Id: I99c639bf61ce2151b85fbf08e9e55b14663244a7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/spdm/+/5507977
Reviewed-by: Vadim Sukhomlinov <sukhomlinov@google.com>
Tested-by: Howard Yang <hcyang@google.com>
Commit-Queue: Howard Yang <hcyang@google.com>
8 files changed