command list:
        help           this list
        script         run script at specific address
        go             jump directly to address
        bootx          boot a kernel cache at specified address
        diags          boot into diagnostics (if present)
        tsys           boot into tsys (if present)
        bdev           block device commands
        image          flash image inspection
        fs             file system commands
        fsboot         try to boot kernel at /kernelcache
        devicetree     create a device tree from the specified address
        ramdisk        create a ramdisk from the specified address
        tftp           tftp via ethernet to/from device
        eload          tftp via ethernet from hardcoded install server
        halt           halt the system (good for JTAG)
        reboot         reboot the device
        poweroff       power off the device
        md             memory display - 32bit
        mdh            memory display - 16bit
        mdb            memory display - 8bit
        mw             memory write - 32bit
        mwh            memory write - 16bit