msc: rename sub-directory from msc_tests to msc (to be in line with bsc, etc.)

Change-Id: Ib219dee5e587bca3b79d29d631836cf1ef2be81c
diff --git a/Makefile b/Makefile
index 80211de..f009560 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-SUBDIRS=bsc bsc-nat ggsn_tests gprs_gb lapdm mgw msc_tests selftest sysinfo
+SUBDIRS=bsc bsc-nat ggsn_tests gprs_gb lapdm mgw msc selftest sysinfo
 
 PARALLEL_MAKE:=-j4