mtd: nand: am335x: Fix 'bit-flip' errors in SPL

mtd: nand: am335x: Fix 'bit-flip' errors in SPL

OMAP GPMC driver used with some NAND Flash devices
(e.g. Spansion S34ML08G1) causes that U-boot shows
hundreds of 'nand: bit-flip corrected' error messages.
Possible cause was discussed in the mailinglist thread:
http://lists.denx.de/pipermail/u-boot/2014-April/177508.html

The issue was partially fixed with the cc81a5291910d7a.git
however this has to be done to fix the SPL.

The original author of the code is Belisko Marek
<marek.belisko@gmail.com>

Signed-off-by: Rostislav Lisovy <lisovy@merica.cz>