Added code gen regression test for avx512 instructions scheduling called avx512-schedule.ll
This patch is in preparation of a larger patch of adding all SKX instruction scheduling and therefore
the scheduling for the avx512 instructions are still missing.
The avx512-schedule.ll test was formed from the following tests:
avx512bw-intrinsics.ll
avx512bwvl-intrinsics.ll
avx512cd-intrinsics.ll
avx512cdvl-intrinsics.ll
avx512dq-intrinsics.ll
avx512dqvl-intrinsics.ll
avx512-fma-intrinsics.ll
avx512-gather-scatter-intrin.ll
avx512-intrinsics.ll
avx512vpopcntdq-intrinsics.ll