* Improve the error logging if a file is too large and truncated.
* Increase the maximum size of the ramdisk to 96MB.
* Preliminary changes to expose the boot-mode used to load the
ramdisk via device-tree.
N.B. Secure boot is only recommended for industrial customers and is
currently a beta release. This can only be enabled via RPIBOOT
https://github.com/raspberrypi/usbboot/blob/master/Readme.md
