Make PrebuiltEtcHostFactory public.

Bug: 122332220
Test: prebuilt_etc_test.go + manual builds
Change-Id: Ia2f882f0d18f3f06f396b2bf3f3052d27c6ab96d
diff --git a/android/prebuilt_etc_test.go b/android/prebuilt_etc_test.go
index f31fc9e..d0961a7 100644
--- a/android/prebuilt_etc_test.go
+++ b/android/prebuilt_etc_test.go
@@ -28,7 +28,7 @@
 	defer tearDown(buildDir)
 	ctx := NewTestArchContext()
 	ctx.RegisterModuleType("prebuilt_etc", ModuleFactoryAdaptor(PrebuiltEtcFactory))
-	ctx.RegisterModuleType("prebuilt_etc_host", ModuleFactoryAdaptor(prebuiltEtcHostFactory))
+	ctx.RegisterModuleType("prebuilt_etc_host", ModuleFactoryAdaptor(PrebuiltEtcHostFactory))
 	ctx.PreDepsMutators(func(ctx RegisterMutatorsContext) {
 		ctx.BottomUp("prebuilt_etc", prebuiltEtcMutator).Parallel()
 	})