net: phy: ksz90x1: Simplify ksz9131_config_rgmii_delay

We can call phy_modify_mmd() instead of manually calling drv->readext()
and drv->writeext().

Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
1 file changed