cros-board: add chiron and arion boards

BUG=b/150818201
TEST=cusky presubmit
RELEASE_NOTE=None

Change-Id: I1341ea73e5cd3c78947228e67c1336e299b98a2c
diff --git a/eclass/cros-board.eclass b/eclass/cros-board.eclass
index 1b46d63..f07cf73 100644
--- a/eclass/cros-board.eclass
+++ b/eclass/cros-board.eclass
@@ -42,6 +42,7 @@
 	aplrvp
 	#app-shell-panther
 	aries
+	arion
 	arkham
 	arm-generic
 	#arm-generic_freon
@@ -107,6 +108,7 @@
 	cheza-freedreno
 	cheza64
 	cheza64-freedreno
+	chiron
 	#chronos
 	cid
 	clapper