ARM: i.MX6: add ethernet phy fixup for KSZ9031

The KSZ9031 is used on the i.MX6 based Data Modul eDM-QMX6
board. It needs the same fixup to the rx/tx delays as other
i.MX6 boards.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>