af-packet: remove non-mmap tpacket-v1 support
The af-packet code supports 3 main modes of capture:
- non-mmap'd with tpacket-v1
- mmap with tpacket-v2
- mmap with tpacket-v3
I think the first can safely be removed. If ppl don't care about performance they can fall back to using
TPACKET_V2 was introduced into the linux kernel in 2008, with some 2.6 kernel version. I think we can assume all supported systems to have at least v2.