ice/ptp: fix crosstimestamp reporting

ice/ptp: fix crosstimestamp reporting

Set use_nsecs=true as timestamp is reported in ns. Lack of this result
in smaller timestamp error window which cause error during phc2sys
execution on E825 NICs:
phc2sys[1768.256]: ioctl PTP_SYS_OFFSET_PRECISE: Invalid argument

This problem was introduced in the cited commit which omitted setting
use_nsecs to true when converting the ice driver to use
convert_base_to_cs().

Testing hints (ethX is PF netdev):
phc2sys -s ethX -c CLOCK_REALTIME  -O 37 -m
phc2sys[1769.256]: CLOCK_REALTIME phc offset -5 s0 freq      -0 delay    0

Fixes: d4bea547ebb57 ("ice/ptp: Remove convert_art_to_tsc()")
Signed-off-by: Anton Nadezhdin <anton.nadezhdin@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Tested-by: Rinitha S <sx.rinitha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>