Fixing ethernet driver compilation error for i.MX31 ADS board

This is only a partial revert of "ARM: mx3/mx31ads: fold board
header in its only user"
[commit ccfa7c26)]

As some of the the board defines are also used in the cs89x0
ethernet driver by the i.MX31 ADS.

Signed-off-by: Ian Lartey <ian@opensource.wolfsonmicro.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>