Add section/priority for source package

Change-Id: Icac9ea7a2e0c75dd0739ebcb1661ddc03dda2b16
diff --git a/debian/control b/debian/control
index a969855..300def7 100644
--- a/debian/control
+++ b/debian/control
@@ -1,4 +1,6 @@
 Source: imx-atf
+Section: misc
+Priority: optional
 Maintainer: AIY Projects <support-aiyprojects@google.com>
 Build-Depends: debhelper