netdev: octeon_mgmt: Add hardware timestamp support.

netdev: octeon_mgmt: Add hardware timestamp support.

Octeon cn6XXX models have timestamp support on the mgmt ports, so hook
it up.

Signed-off-by: Chad Reese <kreese@caviumnetworks.com>
Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Cc: David S. Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Cc: linux-k3rnel@vger.kernel.org,
Patchwork: https://patchwork.linux-mips.org/patch/4285/
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>