ARCH: OMAP: Kill compile warning on board-3430sdp-flash.c

Commit 3ae4b7e31cd51af2e2184c640c9f50f574acd449 from Adrian Hunter
has changed onenand_setup prototype in struct omap_onenand_platform_data
causing a compile warning of incompatible pointer type when building
3430sdp kernels.

This is a trivial patch to fix such warning.

Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>