Remove empty DepsMutator methods

Add an empty DepsMutator to ModuleBase so it doesn't have to be
implemented on every module that doesn't need it.

Test: all soong tests
Change-Id: I545a832a0dbf27386d3080377a75ea482cd9ce59

python/defaults.go

@@ -30,9 +30,6 @@ type Defaults struct {
 func (d *Defaults) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 }
 
-func (d *Defaults) DepsMutator(ctx android.BottomUpMutatorContext) {
-}
-
 func defaultsFactory() android.Module {
 	return DefaultsFactory()
 }