pch_gbe: correct receive time stamp filtering

This patch fixes the driver so that multicast PTP event messages can
be recognized by the hardware time stamping unit. The station address
register must be set according to the desired transport type.

[ RC - Rebased Takahiro's changes and wrote a commit message
  explaining the changes. ]

Signed-off-by: Takahiro Shimizu <tshimizu818@gmail.com>
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>