msc_vlr_tests: make all test functions static

All functions in the individual msc_vlr_test_*.c files should be static; hence
we would be warned if one of them were unused (forgotten to add to the tests
array).

Change-Id: Ia169c6a1443a48879ab4777e09c2040c48810bf6
diff --git a/tests/msc_vlr/msc_vlr_test_rest.c b/tests/msc_vlr/msc_vlr_test_rest.c
index c19c4c6..1a403c3 100644
--- a/tests/msc_vlr/msc_vlr_test_rest.c
+++ b/tests/msc_vlr/msc_vlr_test_rest.c
@@ -23,7 +23,7 @@
 
 #include "msc_vlr_tests.h"
 
-void test_early_stage()
+static void test_early_stage()
 {
 	comment_start();
 
@@ -62,7 +62,7 @@
 	comment_end();
 }
 
-void test_cm_service_without_lu()
+static void test_cm_service_without_lu()
 {
 	comment_start();
 
@@ -78,7 +78,7 @@
 	comment_end();
 }
 
-void test_two_lu()
+static void test_two_lu()
 {
 	comment_start();
 
@@ -150,7 +150,7 @@
 	comment_end();
 }
 
-void test_lu_unknown_tmsi()
+static void test_lu_unknown_tmsi()
 {
 	comment_start();