Separate system_ext_hwservice_contexts out of system sepolicy.

Bug: 137712473
Test: boot crosshatch
Change-Id: Ic5774da74e200b9d7699ac2240a12e7616dc512a
diff --git a/Android.bp b/Android.bp
index 5dd8628..170e7ca 100644
--- a/Android.bp
+++ b/Android.bp
@@ -225,6 +225,12 @@
 }
 
 hwservice_contexts {
+    name: "system_ext_hwservice_contexts",
+    srcs: [":hwservice_contexts_files"],
+    system_ext_specific: true,
+}
+
+hwservice_contexts {
     name: "product_hwservice_contexts",
     srcs: [":hwservice_contexts_files"],
     product_specific: true,