net: smsc911x: augment device tree bindings

This adds device tree bindings for:

- An optional GPIO line for releasing the RESET signal to the
  SMSC911x devices

- An optional PME (power management event) interrupt line that
  can be utilized to wake up the system on network activity.
  This signal exist on all the SMSC911x devices, it is just not
  very often routed.

Both these lines are routed to the SoC on the Qualcomm APQ8060
Dragonboard and thus needs to be bound in the device tree.

Cc: devicetree@vger.kernel.org
Cc: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>