tg3: PTP - Add the hardware timestamp ioctl

This patch implements the SIOCSHWTSTAMP ioctl as described in
Documentation/networking/timestamping.txt

[Removed HWTSTAMP_FILTER_ALL handling by returning -ERANGE based on input
 from Richard Cochran.]

Signed-off-by: Nithin Nayak Sujir <nsujir@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>