The ornamental design for a frontportion of a motor vehicle, as shown and described.
FIG. 1 is a perspective view of a front portion of a motor vehicle;
FIG. 2 is an enlarged perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a left side view thereof; and,
FIG. 6 is a top view thereof.
The de-emphasized and halftone portions shown in the drawings illustrate environmental structure for the front portion of a motor vehicle that forms no part of the claimed design.