merge request for MLO to boot PocketBeagle

[SAITOU Toshihide]

To boot PocketBeagle, we need a patch to MLO which supplied[2].
How do I request to merge this for the snapshot image.
(sysutils/u-boot-beaglebone looks doesn't exist now.)

[1] https://mail-index.netbsd.org/port-arm/2017/10/23/msg004423.html
[2] 
https://eewiki.net/display/linuxonarm/PocketBeagle#PocketBeagle-Bootloader:U-Boot
[3] http://www.netbsd.org/~sevan/pocketbeagle-ub-2017-09.tgz


Thanks.

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SAITOU Toshihide