The ornamental design for an anchoringdevice, as shown and described.
FIG. 1 is a top view of the anchoring device;
FIG. 2 is a bottom view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a back view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof; and,
FIG. 7 is an isometric view thereof.
The broken line showing of aspects of the anchoring device in FIG. 2 is included for the purpose of illustrating environment and forms no part of the claimed design.