<nvidia_folder>/Linux_for_Tegra/sources/u-boot
It will create u-boot.bin.
$ ./compile_u-boot.sh
- Copy u-boot.bin to:
<nvidia_folder>/Linux_for_Tegra/bootloader/t210ref/p3450-0000/u-boot.bin
- flash new u-boot partition into device.
$ sudo ./flash.sh -r -k LNX jetson-nano-devkit-emmc mmcblk0p1