dt-bindings: net: phy: Add support for NXP TJA11xx

Document the NXP TJA11xx PHY bindings.

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>