net: phy: bcm7xxx: Add an entry for BCM72113

BCM72113 features a 28nm integrated EPHY, add an entry to the driver for
it.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>