net: ethernet: davinci_emac: add OF support

add OF support for the davinci_emac driver.

Signed-off-by: Heiko Schocher <hs@denx.de>
Acked-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Cc: netdev@vger.kernel.org
Cc: davinci-linux-open-source@linux.davincidsp.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: devicetree-discuss@lists.ozlabs.org
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Sekhar Nori <nsekhar@ti.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Anatoly Sivov <mm05@mail.ru>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>