phy: phy_{read|write}_mmd_indirect: get addr from phydev

The address of the device can be determined from the phydev structure,
rather than passing it as a parameter.

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