The ornamental design for an instrumentpanel for a motor vehicle, as shown and described.
FIG. 1 is a perspective view of an instrument panel for a motor vehicle;
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; and,
FIG. 7 is a bottom view thereof.
The dash-dash broken lines and de-emphasized in half-tone portions illustrate portions of the instrument panel for a motor vehicle that form no part of the claimed design.