Flex-OneNAND support

Hi,

This is a repost of support for Flex-OneNAND devices.

Changes since v1(last post):
- Rebased to u-boot-nand-flash.
- Updated review comments from MTD list.
- Support eraseregions with odd number of blocks.
- JFFS2 commands support for Flex-OneNAND.

I have split the patches so that it is more readable.

patch 1 : Flex-OneNAND driver
patch 2 : Environment support for Flex-OneNAND patch 3 : JFFS2 commands support for Flex-OneNAND patch 4 : Flex-OneNAND boundary setting command

Any comments are appreciated.
Thanks,
Rohit