cmd: nand biterr - Add support for nand biterr command

cmd: nand biterr - Add support for nand biterr command

The command shall be used to induce bit errors in the nand page
manually. The code flips a bit in the specified offset without
changing the ECC. This helps to see how the software handles the
error.

The patch is ported from
https://patchwork.ozlabs.org/project/uboot/patch/\
1325691123-19565-1-git-send-email-holger.brunck@keymile.com

The implementation is inspired from
'mtd-utils/nand-utils/nandflipbits.c'

Signed-off-by: Balamanikandan Gunasundar <balamanikandan.gunasundar@microchip.com>