The ornamental design for a lightingdevice, as shown and described.
FIG. 1 is a perspective rear-bottom view of a lighting device;
FIG. 2 is a perspective frontal-top view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a view from one side thereof;
FIG. 6 is a view from another side thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The broken line showing of portions of the lighting device is included for the purpose of illustrating environmental structure and forms no part of the claimed design.