net: gmac_rockchip: Add handling for RGMII_ID/RXID/TXID

net: gmac_rockchip: Add handling for RGMII_ID/RXID/TXID

Using PHY internal delays in combination with the phy-mode
rgmii-id/rxid/txid was not possible. Only rgmii was supported.

Now we can disable rockchip's gmac delay lines and also use
rgmii-id/rxid/txid.

Based on commit eaf70ad14cbb ("net: stmmac: dwmac-rk: Add
handling for RGMII_ID/RXID/TXID") for mainline linux kernel.

Signed-off-by: Janine Hagemann <j.hagemann@phytec.de>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: David Wu <david.wu@rock-chips.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>