net: phy: mdio: add IPQ4019 MDIO driver

This patch adds the driver for the MDIO interface
inside of Qualcomm IPQ40xx series SoC-s.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Cc: Luka Perkov <luka.perkov@sartura.hr>
Signed-off-by: David S. Miller <davem@davemloft.net>