MAINTAINERS: Add myself as third phylib maintainer

Add myself as third phylib maintainer.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -5534,6 +5534,7 @@ F:	net/bridge/
 ETHERNET PHY LIBRARY
 M:	Andrew Lunn <andrew@lunn.ch>
 M:	Florian Fainelli <f.fainelli@gmail.com>
+M:	Heiner Kallweit <hkallweit1@gmail.com>
 L:	netdev@vger.kernel.org
 S:	Maintained
 F:	Documentation/ABI/testing/sysfs-bus-mdio