The ornamental design for a deviceholder, as shown and described.
FIG. 1 is a front, top perspective view of the device holder, showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a back, bottom perspective view thereof.
The broken line showing of the electronic device seen in FIG. 1 is included for the purpose of illustrating environment of the article and forms no part of the claimed design.