Adjust ISecureStorage vintf target

It's cleaner to use vintf_fragment for vintf file.

Bug: 377520831
Test: m
Test: atest vts_treble_vintf_vendor_test
Change-Id: Ibafe5e94cd58424fd9db5e11868caa66ea76480f
diff --git a/security/see/storage/default/Android.bp b/security/see/storage/default/Android.bp
index 7ea7739..33d93bb 100644
--- a/security/see/storage/default/Android.bp
+++ b/security/see/storage/default/Android.bp
@@ -13,9 +13,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-prebuilt_etc {
+vintf_fragment {
     name: "android.hardware.security.see.storage-service.trusty.xml",
-    sub_dir: "vintf",
-    vendor: true,
     src: "android.hardware.security.see.storage-service.trusty.xml",
+    vendor: true,
 }