ARM: OMAP2+: remove legacy support for IGEP boards

Device Tree support for IGEP boards in mainline is almost
finished. The only remaining bits are support for the
Marvell SD8686 wifi + BT and TFP410 DVI chips.

Adding support for these should be straightforward so let's
not block OMAP3 moving to Device Tree only boot and remove
the board file for IGEP boards.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>