Add required BY_EXCEPTION_ONLY header comment. am: 1ee4a096eb am: 77cf8485d5 am: 9bfbf09aee

Original change: https://android-review.googlesource.com/c/platform/external/ms-tpm-20-ref/+/1559290

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I02a07ef5ac6d33f2b716f4788c1b15bfac17b0ab