net/af_packet: run on kernel without qdisc bypass support

net/af_packet: run on kernel without qdisc bypass support

Some older kernels do not support the PACKET_QDISC_BYPASS socket
option. Such an example is the CentOS 7 kernel (3.10).

If we only check for the definition of PACKET_QDISC_BYPASS, it might mean
that we will not be able to compile the PMD driver on a newer platform,
and run in on a machine with an older kernel.

Setting the socket option only if it is specifically requested from
the EAL arguments, allows us to have a way to run the PMD compiled
against newer kernel headers, on platforms having older kernels.

Signed-off-by: Tudor Cornea <tudor.cornea@keysight.com>
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>