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/cc.go b/cc/cc.go
index 75292aa..791d9ea 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -26,14 +26,13 @@
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
 
-	"android/soong"
 	"android/soong/android"
 	"android/soong/cc/config"
 	"android/soong/genrule"
 )
 
 func init() {
-	soong.RegisterModuleType("cc_defaults", defaultsFactory)
+	android.RegisterModuleType("cc_defaults", defaultsFactory)
 
 	// LinkageMutator must be registered after common.ArchMutator, but that is guaranteed by
 	// the Go initialization order because this package depends on common, so common's init