snapshots/devmapper: don't hardcord the platform strings

The snapshotter doesn't have to exclude non-amd64 platforms.

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

snapshots/devmapper/snapshotter.go

@@ -30,12 +30,12 @@ import (
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/log"
 	"github.com/containerd/containerd/mount"
+	"github.com/containerd/containerd/platforms"
 	"github.com/containerd/containerd/plugin"
 	"github.com/containerd/containerd/snapshots"
 	"github.com/containerd/containerd/snapshots/devmapper/dmsetup"
 	"github.com/containerd/containerd/snapshots/storage"
 	"github.com/hashicorp/go-multierror"
-	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 )
@@ -46,10 +46,7 @@ func init() {
 		ID:     "devmapper",
 		Config: &Config{},
 		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
-			ic.Meta.Platforms = append(ic.Meta.Platforms, ocispec.Platform{
-				OS:           "linux",
-				Architecture: "amd64",
-			})
+			ic.Meta.Platforms = append(ic.Meta.Platforms, platforms.DefaultSpec())
 
 			config, ok := ic.Config.(*Config)
 			if !ok {