I am running Current on an x230 with coreboot and do not have a problem with the usb 3.0 port. I haven't updated coreboot for awhile, so either they changed something or your build config needs to be modified (my guess is the latter).
$ dmesg | grep coreboot bios0: vendor coreboot version "CBET4000 4.5-1440-geb1bdd8-dirty" date 03/29/2017
