VZEROUPPER should not be issued on Knights Landing (KNL) , but on Skylake-avx512 it should be.
Modified the x86vzeroupper pass to support that.
A lot of LIT tests had to be modified, most of them were fixed automatically by regenerating the "CHECK" lines using update_llc_test_checks.py.
Other changes are name changing to illustrate that VZEROUPPER is needed for zmm as well as ymm.