ARM: dts: omap4-sdp: Make ethernet working even if booted with latest u-boot

The ethernet works in kernel only if we use some binary u-boot from the
past which have support for KS8851.

The u-boot sources are not available for this mysterious u-boot image
people tends to hold on... Mainline u-bott does not have ethernet support
for sdp4430 and if we use that the ethernet is not working.

After some debugging I have managed to get the ethernet working with
mainline u-boot while not breaking the networking with the case when we
boot with the mysterious binary u-boot.

Basically we were missing bunch of pinmux settings and the 'magic'
gpio_138 handling in kernel.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>