doc: Add a new migration guide entry to ethernet

Add the following property renaming entries to
the migration:

* location-phy_mdc
* location-phy_mdio
* location-rmii_refclk
* location-rmii_crs_dv
* location-rmii_txd0
* location-rmii_txd1
* location-rmii_tx_en
* location-rmii_rxd0
* location-rmii_rxd1
* location-rmii_rx_er
* location-phy_pwr_enable
* location-phy_reset
* location-phy_interrupt

Signed-off-by: James Roy <rruuaanng@outlook.com>