net: mdio-mux: printing driver version is useless

Remove the driver version information because this information
is not useful in an upstream kernel driver.

Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>