Revert "Simplify arch target handling"

This reverts commit 6713fb26cbcadf525cd75e47d7d0cbc23d282b3e.

Change-Id: Ic473cea2563b0b37dc08b0bc5d3a0ac8c4b6afe6
diff --git a/cc/arm_device.go b/cc/arm_device.go
index 1624cfc..766eea6 100644
--- a/cc/arm_device.go
+++ b/cc/arm_device.go
@@ -392,5 +392,5 @@
 }
 
 func init() {
-	registerToolchainFactory(android.Android, android.Arm, armToolchainFactory)
+	registerDeviceToolchainFactory(android.Arm, armToolchainFactory)
 }