drivers: ethernet: phy_realtek_rtl8211f: enable RGMII TX/RX delay

The RGMII specifies output TXC/RXC and TXD/RXD without any clock skew.
Need to add skew on clock line to make sure the other side sample
right data. This can also be done in PCB traces.
This patch is to enable RGMII TX/RX delay to ensure timing.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>