Move registration into android package

Mutator registration is tightly coupled with the android package, move
all registration from the soong package to the android package.

Test: build.ninja identical
Change-Id: Ie183d0b52cc7431c9e05b231934d189208ef1efe
diff --git a/cc/ndk_prebuilt.go b/cc/ndk_prebuilt.go
index 407a026..106c9b5 100644
--- a/cc/ndk_prebuilt.go
+++ b/cc/ndk_prebuilt.go
@@ -20,16 +20,15 @@
 
 	"github.com/google/blueprint"
 
-	"android/soong"
 	"android/soong/android"
 	"android/soong/cc/config"
 )
 
 func init() {
-	soong.RegisterModuleType("ndk_prebuilt_library", ndkPrebuiltLibraryFactory)
-	soong.RegisterModuleType("ndk_prebuilt_object", ndkPrebuiltObjectFactory)
-	soong.RegisterModuleType("ndk_prebuilt_static_stl", ndkPrebuiltStaticStlFactory)
-	soong.RegisterModuleType("ndk_prebuilt_shared_stl", ndkPrebuiltSharedStlFactory)
+	android.RegisterModuleType("ndk_prebuilt_library", ndkPrebuiltLibraryFactory)
+	android.RegisterModuleType("ndk_prebuilt_object", ndkPrebuiltObjectFactory)
+	android.RegisterModuleType("ndk_prebuilt_static_stl", ndkPrebuiltStaticStlFactory)
+	android.RegisterModuleType("ndk_prebuilt_shared_stl", ndkPrebuiltSharedStlFactory)
 }
 
 // NDK prebuilt libraries.