drivers: ethernet: phy: add Microchip's KSZ9131 PHY support

Add support for KSZ9131 (Gigabit Ethernet Transceiver with RGMII Support).
As first starter, 100MBit/s mode is tested.
https://www.microchip.com/en-us/product/ksz9131

Signed-off-by: Tony Han <tony.han@microchip.com>
4 files changed