Update include/android_image.h from AOSP

This takes the latest changes from AOSP from the file
include/bootimg/bootimg.h from the repository:
https://android.googlesource.com/platform/system/tools/mkbootimg


and update the U-Boot version with the latest changes.

This file keeps the changes from AOSP to a minimum:
 * Comments were converted from C++ to C style.
 * Code inside __cplusplus #ifdef blocks were removed.
 * C++11 struct extensions replaced with a single struct.

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