pch_gbe: do not set the channel control register

We will let the pch_gbe code do that according to the receive time stamp
filter.

[ 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>