ring: add set_sockopt_tpacket_v3 and refactor others

Add set_sockopt_tpacket_v3() in preparation for TPACKET_V3.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
ring: minor: remove define since only used once

We only use it once and nowhere else, so just replace the correct
value right away.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
ring: move poll related fallback define to built_in.h

It rather belongs to built_in.h, and not here.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>