MIPS: Jz4740: Add NAND driver

Jz4740 NAND flash controller can support:
* MLC NAND as well as SLC NAND
* all 8-bit/16-bit NAND flash devices
* HAMMING and RS hardware ECC
* automatic boot up from NAND flash devices

nand_ecclayout is set up for 2GiB NAND chip mounted in Qi LB60.
We'll bring up boot-from-NAND support in nand_spl/ in the future.

Signed-off-by: Xiangfu Liu <xiangfu@openmobilefree.net>
Acked-by: Daniel <zpxu@ingenic.cn>
Signed-off-by: Shinya Kuribayashi <skuribay@pobox.com>