hwpack: better document am57xx-beagle-x15.conf, that it supports the AI
hwpack: better document am57xx-beagle-x15.conf, that it supports the AI

fixes: https://github.com/RobertCNelson/omap-image-builder/issues/126
Signed-off-by: Robert Nelson <d6c41255011d14bfa93d8562b946ca186cfa0c7b@gmail.com>

RobertCNelson/omap-image-builder,beagleboard/image-builder,RobertCNelson/omap-image-builder,beagleboard/image-builder