ARM: nomadik: fix IRQ assignment for SMC ethernet

The assignment of IRQ for the SMC91x ethernet adapter had two
problems making it non-working:

- It was not put into the ethernet device node. Let's do this
  by using the board-specific overlay, so we can make other
  overlays on other Nomadik boards.

- The IRQ number was actually completely wrong, this was the
  number for NHK8815, not S8815.

After this ethernet starts working on the USB S8815.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>