smpp: Fix the make distcheck for smpp

DISTCHECK_CONFIGURE_FLAGS="--enable-smpp" make distcheck
diff --git a/openbsc/src/libmsc/Makefile.am b/openbsc/src/libmsc/Makefile.am
index c36ba92..2b50599 100644
--- a/openbsc/src/libmsc/Makefile.am
+++ b/openbsc/src/libmsc/Makefile.am
@@ -19,5 +19,6 @@
 			osmo_msc.c
 
 if BUILD_SMPP
+noinst_HEADERS = smpp_smsc.h
 libmsc_a_SOURCES += smpp_smsc.c smpp_openbsc.c smpp_vty.c smpp_utils.c
 endif
diff --git a/openbsc/tests/smpp/Makefile.am b/openbsc/tests/smpp/Makefile.am
index eb25965..b3d4568 100644
--- a/openbsc/tests/smpp/Makefile.am
+++ b/openbsc/tests/smpp/Makefile.am
@@ -7,6 +7,6 @@
 noinst_PROGRAMS = smpp_test
 
 smpp_test_SOURCES = smpp_test.c \
-	$(top_srcdir)/src/libmsc/smpp_utils.c
+	$(top_builddir)/src/libmsc/smpp_utils.c
 smpp_test_LDADD = $(LIBOSMOCORE_LIBS) \
-	$(top_srcdir)/src/libcommon/libcommon.a
+	$(top_builddir)/src/libcommon/libcommon.a