Instead of verifying the CRC before every access of the boot data,
verify the CRC once at startup and set a flag to indicate the boot
data is valid.
Also add a framework to support multiple boot protocol versions.
Firmware declares the maximum supported protocol version using a
version byte in the boot data header. The bootloader chooses the
highest version supported by it and the firmware when deciding
what boot protocol to use.
Change-Id: I810194625dc0833f026d2a23b8d64ed467fa6aca
The implementation of write_bootdata() and get_redirect_dir() was
copied verbatim in two different places, obviously a bad thing for
maintainability. This moves them to a new file multiboot.c as they
are only used for multiboot.
Change-Id: Id0279216e4dd019f8bf612a81d3835eff010e506
