Fix CSR format for RKPv3

The data format changed a bit, and the fingerprint needs to be included
at the end of the CSRv3 data. Make sure to include that, else the RKP
server rejects the payload.

Test: run tool + upload output
Test: rkp_factory_extraction_lib_test
Change-Id: I5a13b21e65c64f19b9417a7d1e169710867e7a8f
2 files changed