Each entry in BCC is signed by its parent. BCC validator should be able to validate the signature along the chain. In OPK reference, EdDSA is used. Also adding functions to support ECDSA in oemcrypto_ecc_key module. Test: opk_ta_p40 Bug: 300310163 Bug: 307968622 Change-Id: Ibed895933eeb71b18c467604588cca449cac1af9