fec_mpc52xx: enable transmit and receive time stamping.

This patch enables software (and phy device) time stamping. Software
time stamping using the SO_TIMESTAMPING API was tested and found to be
working on the LITE5200B board.

Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
Signed-off-by: David S. Miller <davem@davemloft.net>