When booting an IGEPv2 board from NAND with SPL, U-Boot hangs
trying to read the OMAP General Purpose Memory Controller (GPMC).

The reason is that the GPMC initialization function is called
inside spl_board_init() and this function is only executed when
CONFIG_SPL_BOARD_INIT is defined.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Acked-by: Enric Balletbo i Serra <eballetbo@iseebcn.com>