The driver doesn't support clause 45 register access yet, but doesn't
check if the access is a c45 one either. This leads to spurious register
reads and writes. Add the check.
Fixes: 542671fe4d86 ("net: phy: mscc-miim: Add MDIO driver") Signed-off-by: Michael Walle <michael@walle.cc> Reviewed-by: Andrew Lunn <andrew@lunn.ch> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>