The ornamental design for a device mount, as shown and described.
FIG. 1 is a front perspective view of a device mount;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left-side elevational view thereof;
FIG. 5 is a right-side elevational view thereof;
FIG. 6 is a bottom plan view thereof; and,
FIG. 7 is a top plan view thereof.
The dashed broken lines depict portions of the device mount that form no part of the claimed design. The dot-dashed broken lines represent boundaries of the claimed device mount and form no part of the claimed design.