Fix C reference code in tutorial 5
Fix C reference code in tutorial 5


Former-commit-id: 0b31bb1a9ba1e22f16dd55108c91c1d8aa3a49e5
Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide