tg3: PTP - Add header definitions, initialization and hw access functions.

This patch adds code to write the reference clock. If a chip reset is
performed, the hwclock is reinitialized with the adjusted kernel time

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>