Revert most of the message versioning update.

Bootloaders also communicate with keymaster, and may not get updated
when the TA does.  The message versioning change broke them.  A new
versioning scheme is needed that allows versions to be out of sync in
either direction.  That will come in a future CL.

Bug: 175513064
Test: build.py qemu-generic-arm64-gicv3-test-debug --verbose --test=^boot.*mmutest
Change-Id: I955db95b7808f9efacb0a8b78297c825b6929cd6
3 files changed