mtd: nand/docg4: add support for writing in reliable mode

The controller on the docg4 has a "reliable" mode, where consecutive 2k pages
are used in parallel.  The initial program loader (IPL) on my Treo 680 expects
the secondary program loader (SPL) to be written in this mode.  This patch adds
support for writing data in reliable mode, by way of a module parameter.
Support for reading in this mode (as the IPL does) is not supported yet, but
alternate (even-numbered) 2k pages written in reliable mode can be read normally
(odd-numbered pages will contain junk and generate ecc errors).

Signed-off-by: Mike Dunn <mikedunn@newsguy.com>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>