ARM: OMAP3: igep0020: Add support for Micron NAND Flash storage memory

IGEP-based boards can have two different flash memories, a OneNAND or
a NAND device. The boot configuration pins (sys_boot) are used to
specify which memory is available.

Also, this patch removes unnecesary code for registering the OneNAND.

Signed-off-by: Javier Martinez Canillas <javier@dowhile0.org>
Acked-by: Enric Balletbo i Serra <eballetbo@gmail.com>
Tested-by: Enric Balletbo i Serra <eballetbo@gmail.com>
[tony@atomide.com: fixed up a minor checkpatch warning]
Signed-off-by: Tony Lindgren <tony@atomide.com>