net/mlx5: Don't call timecounter cyc2time directly from 1PPS flow

Before calling timecounter_cyc2time(), clock->lock must be taken.
Use mlx5_timecounter_cyc2time instead which guarantees a safe access.

Fixes: afc98a0b

 ("net/mlx5: Update ptp_clock_event foreach PPS event")
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>