ARM: dts: omap3-igep0020: Add SMSC911x LAN chip support

The IGEPv2 board has an SMSC LAN9221i ethernet chip connected to
the OMAP3 processor though the General-Purpose Memory Controller.

This patch adds a device node for the ethernet chip as a GPMC child
and all its dependencies (regulators, GPIO and pin muxs).

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>