Import include/android_bootloader_message.h from AOSP

Import include/android_bootloader_message.h from AOSP

This takes the latest changes from AOSP from the file
bootloader_message/include/bootloader_message/bootloader_message.h
in the repository
https://android.googlesource.com/platform/bootable/recovery
and re-licensed them to BSD-3 for U-Boot.

Minimum local changes have been applied (convert C++ to C comments and
adding #ifndef __UBOOT__ block to skip all the function declarations).

Signed-off-by: Alex Deymo <deymo@google.com>
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>