net: phy: dp83td510: Add support for the DP83TD510 Ethernet PHY

The DP83TD510E is an ultra-low power Ethernet physical layer transceiver
that supports 10M single pair cable.

This driver was tested with NXP SJA1105, STMMAC and ASIX AX88772B USB Ethernet
controller.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>