Remove dead code in pf_pull_hdr().

Remove dead code in pf_pull_hdr().

pf_pull_hdr() allows to pass an action pointer parameter as output
value.  This is never used, all callers pass a NULL argument.  Remove
ACTION_SET() entirely.

The logic (fragoff >= len) in pf_pull_hdr() does not work since
revision 1.4.  Before it was used to drop short TCP or UDP fragments
that contained only part of the header.  Current code in pf_pull_hdr()
drops the packets anyway, so always set reason PFRES_FRAG.

OK kn@ sashan@