What lsusb shows? I think it's quite hard to brick it. The DnX loader, I suspect, should be somewhere deeper than area for IFWI. If this is correct, xfstk might rescue it.
UPDATE. Oh, missed that you are able to get into U-Boot command prompt! So, it doesn't bricked at all. As I said, xfstk will do the job. Just run flashall.sh script with --recovery (? I don't remember) parameter.
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