pcapng: fix timestamp wrapping in output files

pcapng: fix timestamp wrapping in output files

In pcap_tsc_to_ns(), delta * NSEC_PER_SEC will overflow approx 8
seconds after pcap_init is called when using a TSC with a frequency
of 2.5GHz.

To avoid the overflow, update the saved time and TSC value once
delta >= tsc_hz.

Fixes: 8d23ce8f5ee ("pcapng: add new library for writing pcapng files")
Cc: stable@dpdk.org
Signed-off-by: Quentin Armitage <quentin@armitage.org.uk>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>