nat: Fix compilation with nat not being enabled.

common_vty.c was including bsc_nat.h which tried to
get the sccp/sccp_types.h which is not required to be
installed. Move all structs using/embedding SCCP structures
into the bsc_nat_sccp.h and include. This should fix
the compilation.
diff --git a/openbsc/src/nat/bsc_filter.c b/openbsc/src/nat/bsc_filter.c
index 8f79f00..3e92abd 100644
--- a/openbsc/src/nat/bsc_filter.c
+++ b/openbsc/src/nat/bsc_filter.c
@@ -22,6 +22,7 @@
  */
 
 #include <openbsc/bsc_nat.h>
+#include <openbsc/bsc_nat_sccp.h>
 #include <openbsc/ipaccess.h>
 #include <openbsc/debug.h>
 
diff --git a/openbsc/src/nat/bsc_mgcp_utils.c b/openbsc/src/nat/bsc_mgcp_utils.c
index 32d988e..00b7d6d 100644
--- a/openbsc/src/nat/bsc_mgcp_utils.c
+++ b/openbsc/src/nat/bsc_mgcp_utils.c
@@ -20,6 +20,7 @@
  */
 
 #include <openbsc/bsc_nat.h>
+#include <openbsc/bsc_nat_sccp.h>
 #include <openbsc/gsm_data.h>
 #include <openbsc/debug.h>
 #include <openbsc/mgcp.h>
diff --git a/openbsc/src/nat/bsc_nat.c b/openbsc/src/nat/bsc_nat.c
index 0a37193..b47d7ce 100644
--- a/openbsc/src/nat/bsc_nat.c
+++ b/openbsc/src/nat/bsc_nat.c
@@ -39,6 +39,7 @@
 #include <openbsc/debug.h>
 #include <openbsc/bsc_msc.h>
 #include <openbsc/bsc_nat.h>
+#include <openbsc/bsc_nat_sccp.h>
 #include <openbsc/ipaccess.h>
 #include <openbsc/abis_nm.h>
 #include <openbsc/vty.h>
diff --git a/openbsc/src/nat/bsc_nat_utils.c b/openbsc/src/nat/bsc_nat_utils.c
index 5418dc1..bb5ee94 100644
--- a/openbsc/src/nat/bsc_nat_utils.c
+++ b/openbsc/src/nat/bsc_nat_utils.c
@@ -23,6 +23,7 @@
  */
 
 #include <openbsc/bsc_nat.h>
+#include <openbsc/bsc_nat_sccp.h>
 #include <openbsc/bsc_msc.h>
 #include <openbsc/gsm_data.h>
 #include <openbsc/debug.h>
diff --git a/openbsc/src/nat/bsc_nat_vty.c b/openbsc/src/nat/bsc_nat_vty.c
index 0345360..b173463 100644
--- a/openbsc/src/nat/bsc_nat_vty.c
+++ b/openbsc/src/nat/bsc_nat_vty.c
@@ -21,6 +21,7 @@
 
 #include <openbsc/vty.h>
 #include <openbsc/bsc_nat.h>
+#include <openbsc/bsc_nat_sccp.h>
 #include <openbsc/bsc_msc.h>
 #include <openbsc/gsm_04_08.h>
 #include <openbsc/mgcp.h>
diff --git a/openbsc/src/nat/bsc_sccp.c b/openbsc/src/nat/bsc_sccp.c
index 33ab51d..f67e4ad 100644
--- a/openbsc/src/nat/bsc_sccp.c
+++ b/openbsc/src/nat/bsc_sccp.c
@@ -22,6 +22,7 @@
 
 #include <openbsc/debug.h>
 #include <openbsc/bsc_nat.h>
+#include <openbsc/bsc_nat_sccp.h>
 
 #include <sccp/sccp.h>