ep93xx: set DMA masks for the ep93xx_eth

Since the driver uses the DMA API, we should pass it valid DMA masks.

Signed-off-by: Mika Westerberg <mika.westerberg@iki.fi>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Tested-by: Petr Stetiar <ynezz@true.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>