Rename halide_x86_cpuid -> x86_cpuid_halide
Rename halide_x86_cpuid -> x86_cpuid_halide

The “halide_” prefix was causing the name to get left in the final
output, causing lesson_15 to fail.

jiawen/Halide,ronen/Halide,kgnk/Halide,psuriana/Halide,ronen/Halide,jiawen/Halide,ronen/Halide,jiawen/Halide,psuriana/Halide,psuriana/Halide,kgnk/Halide,kgnk/Halide,kgnk/Halide,ronen/Halide,kgnk/Halide,jiawen/Halide,kgnk/Halide,psuriana/Halide,ronen/Halide,ronen/Halide,kgnk/Halide,jiawen/Halide,ronen/Halide,ronen/Halide,psuriana/Halide,psuriana/Halide,kgnk/Halide,jiawen/Halide,psuriana/Halide,jiawen/Halide