Key{Master,Mint}: stricter parameter checking

 - reject more than 2KiB of entropy (both KeyMaster and KeyMint AIDL specs
   require >2KiB to be rejected; the KeyMint VTS test now checks this)
 - check that HMAC length is a multiple of 8
 - check that an attestation challenge is provided whenever an attestion
   key is included
 - in KeyMint mode, strip out any locally-generated CREATION_DATETIME
   tag (but return any value that came from the request)
 - allow EARLY_BOOT key creation but not import

Test: VtsAidlKeyMintTargetTest
Change-Id: I77bcc13cbf096a531d13f85a94d19a16cb812a43
6 files changed