ARM: nomadik: convert SMSC91x ethernet to device tree

This converts the SMSC91x ethernet controller to use device
tree. The existing solution from the board file, to request the
GPIO triggering the ethernet IRQ from the board file is kept
for the time being, but the GPIO number assignment is moved
over to the device tree.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>