Add instructions for Boot from NAND flash

[nikhil-zinjurde-imgtec]

Notes from technical documentation

Writing UBIFS image to Flash

For setting up a tftp server on your development machine, please refer TFTP Boot section above.

Instructions are as follows :-

sf probe 1:0 && dhcp
mtdpart default && nand erase.part firmware0
setenv serverip < dev_PC_IP > && tftpboot 0xe000000 openwrt-pistachio-marduk-marduk_cc2520-ubifs.img
nand write 0xe000000 firmware0 ${filesize};
setenv nandroot "ubi.mtd=firmware0 root=ubi0:rootfs rootfstype=ubifs" && setenv bootcmd 'run nandboot' && saveenv

[nikhil-zinjurde-imgtec]

Done, added in https://github.com/IMGCreator/openwrt