[MTD] TXx9 SoC NAND Flash Memory Controller driver

This patch adds support for the integrated NAND flash controller of the
TXx9 family.

Once upon a time there were tx4925ndfmc and tx4938ndfmc driver.  They
were removed due to bitrot in 2005.
This new driver is completely rewritten based on a driver in CELF patch
archive.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: Ralf Bächle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>