The dp83640 PHY provides time stamp and other information via special
PHY status frames. Previously, the driver decoded the frames and then
let the network stack drop them. This works fine when the PTP messages
come over UDP.

However, when receiving PTP messages via L2 packets, this creates a
problem. The status frames use the official PTP destination MAC address,
and so they are delivered to user space along with the "real" frames,
causing confusion for applications.

This commit fixes the issue by simply dropping the PHY status frames
in the driver.
Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
Signed-off-by: David S. Miller <davem@conan.davemloft.net>