U-Boot loader for BeagleBone and BeagleBone Black.

To install this bootloader, copy the files MLO and bb-uboot.img to the FAT
partition on an SD card or the eMMC.  Normally this is partition 1, but
different partitions can be set with U-Boot environment variables.

This version is patched so that:
 * ELF and API features are enabled.
 * The default environment is trimmed to just what's needed to boot.
 * The saveenv command writes to the file uboot.env on the FAT partition.
 * The DTB file name is chosen based on the board model and passed to ubldr
   using the fdtfile env variable.  ubldr loads the DTB from /boot/dtb/ on
   the FreeBSD partition.
 * By default, it loads ELF ubldr from file bbubldr on the FAT partition
   to address 0x88000000, and launches it.

Note: prefixing the boot files with 'bb' allows building
images with boot bits for more than one board.

For information about running FreeBSD on BeagleBone or BeagleBone Black, see
 https://wiki.freebsd.org/FreeBSD/arm/BeagleBone

For general information about U-Boot see WWW: http://www.denx.de/wiki/U-Boot