mtd: nand: add support for diskonchip G4 nand flash device

This patch adds a driver for the M-Sys / Sandisk diskonchip G4 nand flash found
in various smartphones and PDAs, among them the Palm Treo680, HTC Prophet and
Wizard, Toshiba Portege G900, Asus P526, and O2 XDA Zinc.  It was tested on the
Treo 680, but should work generically.

Since v3, this patch adds power management functions, a scan of the factory bad
block table during initialization, several fixes, and more extensive testing.
Also, the platform data header file, which only contained partitioning
information, was removed.  Command-line partitioning can be used, at least until
an mtd parser is written for the saftl format with which these chips are
shipped.

Signed-off-by: Mike Dunn <mikedunn@newsguy.com>
Reviewed-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>