Fix compile issue with Werror:

nf_conntrack_rtsp.c:667:39: error: implicit declaration of function 'nf_ct_zone' [-Werror=implicit-function-declaration]
   exp_ct = nf_ct_expect_find_get(net, nf_ct_zone(ct), &t);

Fix compile warning:

nf_conntrack_rtsp.c:474:2: warning: enumeration value 'IP_CT_DIR_MAX' not handled in switch [-Wswitch]
  switch (CTINFO2DIR(ctinfo)) {
  ^~~~~~

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>