pcu: Rename 'gprs_gb/Test' tp 'pcu/PCU_Tests' to align with other suites

Change-Id: Ia3350e7e1a9d6715ab81f4a5f413b7e4d728ff60
diff --git a/Makefile b/Makefile
index 8cdbbec..0defc31 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-SUBDIRS=bsc bsc-nat bts ggsn_tests gprs_gb hlr lapdm mgw msc selftest sgsn sysinfo
+SUBDIRS=bsc bsc-nat bts ggsn_tests hlr lapdm mgw msc pcu selftest sgsn sysinfo
 
 PARALLEL_MAKE ?= -j8