net: mscc: use the PHY MII ioctl interface when possible

Allow ioctl to be implemented by the PHY, when a PHY is attached to the
Ocelot switch. In case the ioctl is a request to set or get the hardware
timestamp, use the Ocelot switch implementation for now.

Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>