net: fec: report correct hardware stamping info to ethtool

Report correct hardware stamping capability by ethtool interface.
The v1.0 ptp4l check it.

Signed-off-by: Frank Li <Frank.Li@freescale.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>