ARM: imx6q: remove part of ar8031_phy_fixup()

This part of this fixup is overwritten by at803x_config_init() in
drivers/net/phy/at803x.c. No additional devicetree fixes are needed.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>