net/pcap: propagate timestamp from header to mbuf

net/pcap: propagate timestamp from header to mbuf

Timestamp is always set in PCAP header, whether it reads a file or
listen on an interface. This information can be important for some
applications and it cannot be obtained otherwise (especially when
reading a PCAP file, where the timestamp is not the current time).
Timestamp here is the number of microseconds since epoch.

Signed-off-by: Sylvain Rodon <srn@nexatech.fr>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>