libbt-vendor: add minimum vendor-specific shutdown support

Without this support, the BT shutdown process takes 3 seconds.

Change-Id: I81a8018de7fc005cc6d142803eaa3898367c7348
Signed-off-by: Toshi Kikuchi <toshik@google.com>
diff --git a/libbt-vendor/bt_vendor_mrvl.c b/libbt-vendor/bt_vendor_mrvl.c
index e1e58d5..e3dd48c 100644
--- a/libbt-vendor/bt_vendor_mrvl.c
+++ b/libbt-vendor/bt_vendor_mrvl.c
@@ -143,6 +143,10 @@
 		break;
 	case BT_VND_OP_LPM_WAKE_SET_STATE:
 		break;
+	case BT_VND_OP_EPILOG:
+		if (vnd_cb)
+			vnd_cb->epilog_cb(BT_VND_OP_RESULT_SUCCESS);
+		break;
 	default:
 		ret = -1;
 		break;