[MTD] [JEDEC] add support for the ST M29W400DB flash chip

Add support for the ST M29W400DB flash chip.  which is used on the GLAN Tank
NAS.

Signed-off-by: Gordon Farquharson <gordonfarquharson@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>