net: stmmac: meson8b: remove of_get_phy_mode()

devm_stmmac_probe_config_dt() already gets the PHY mode from firmware,
which is stored in plat_dat->phy_interface. Therefore, we don't need to
get it in platform code.

Set dwmac->phy_mode from plat_dat->phy_interface.

Reviewed-by: Michal Kubiak <michal.kubiak@intel.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1tsIGd-005uzr-0C@rmk-PC.armlinux.org.uk


Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>