network - Remove crit_exit/crit_enter wrappers in pf.c

network - Remove crit_exit/crit_enter wrappers in pf.c

* Note I'm talking about exit/enter wrappers, not enter/exit wrappers.
  I believe the enter/exit wrappers can be removed too but for now
  we have to remove the exit/enter wrappers which assumed a critical
  section would be held on entry.

  This is no longer the case.  Since so much of the network stack is
  now threaded callers into PF are not necessarily holding a critical
  section to exit out of.

Reported-by: lentferj, Rumko