srt: Add missing gstsrt.h to noinst_HEADERS

Reorder the list to match the SOURCES.

https://bugzilla.gnome.org/show_bug.cgi?id=794320
diff --git a/ext/srt/Makefile.am b/ext/srt/Makefile.am
index 02e0d11..bc504f8 100644
--- a/ext/srt/Makefile.am
+++ b/ext/srt/Makefile.am
@@ -30,11 +30,13 @@
 CLEANFILES = $(BUILT_SOURCES)
 
 noinst_HEADERS = \
-	gstsrtbasesink.h \
-	gstsrtclientsink.h  \
-	gstsrtserversrc.h \
+	gstsrt.h \
 	gstsrtbasesrc.h \
 	gstsrtclientsrc.h \
-	gstsrtserversink.h
+	gstsrtserversrc.h \
+	gstsrtbasesink.h \
+	gstsrtclientsink.h  \
+	gstsrtserversink.h \
+	$(NULL)
 
 include $(top_srcdir)/common/gst-glib-gen.mak