Support creation and use of HMAC keys with KM_DIGEST_NONE

KM_DIGEST_NONE should mean "any digest" when applied to HMAC keys,
allowing any valid digest to be specified during begin() of an HMAC
signature or verification operation.

Cherry-picked from internal.

Bug: 22119295
Change-Id: I4698435f5d7aaf0a2f66b9c7aa4097f60c9c6eb3
2 files changed