Using current implementation of polling mode, there is high chances we
will hit into timeout error when running phc2sys. Hence, update the
implementation of hardware crosstimestamping to use the MAC interrupt
service routine instead of polling for TSIS bit in the MAC Timestamp
Interrupt Status register to be set.

Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Wong Vee Khee <vee.khee.wong@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>