The ornamental design for light fixture support, as shown and described.
FIG. 1 is a perspective view of the light fixture support showing my new design;
FIG. 2 is an enlarged view of the light fixture support of FIG. 1;
FIG. 3 front elevational view thereof;
FIG. 4 is a right side elevational view, the left side elevational view being a mirror image;
FIG. 5 is a rear elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken line showing of a light fixture in FIG. 1 is included for the purpose of illustrating environmental structures and forms no part of the claimed design. The broken lines in FIG. 5, which define the bounds of the claimed design, form no part thereof.