omap3: igep0x00: Drop unused SPI support

There are no SPI peripherals in neither the IGEPv2 board nor the IGEP COM
Module, so there's no reason to have this enabled in the boards defconfig.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Enric Balletbo i Serra <eballetbo@gmail.com>