This configuration should be set over device tree.

If this patch breaks network functionality on your system, enable the
AT803X_PHY driver and set following device tree property in the PHY
node:

    qca,clk-out-frequency = <125000000>;
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>