The ornamental design for a controller, as shown and described.
FIG. 1 is a top perspective view of a controller, showing the claimed new design;
FIG. 2 is a bottom perspective view of the controller shown in FIG. 1;
FIG. 3 is a front elevation view of the controller shown in FIG. 1;
FIG. 4 is a rear elevation view of the controller shown in FIG. 1;
FIG. 5 is a side elevation view of the controller shown in FIG. 1;
FIG. 6 is another side elevation view of the controller shown in FIG. 1;
FIG. 7 is a top plan view of the controller shown in FIG. 1; and,
FIG. 8 is a bottom plan view of the controller shown in FIG. 1.
The broken lines immediately adjacent to the shaded portions are boundaries, all other broken lines are environmental structures; all the broken lines form no part of the claimed design.