omap3630: nand: fix device size to work in polled mode

zoom3 and 3630-sdp having the x16 nand device.
This patch configure gpmc as x16 and select the currect function in driver
for polled mode (without prefetch enable) transfer.

Signed-off-by: Sukumar Ghorai <s-ghorai@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>