Remove the dependency on bootloader_message

Now that we move libboot_control to boot/1.1, the definition of
bootloader_message_ab will hide behind the implementation details for
vendor HALs. As this library isn't used in practice, we just inline the
offset here.

Bug: 131775112
Test: build
Change-Id: I64babcad6a421cab5858ab818f392eca196a0fe2
2 files changed