[X86][F16C] Add WriteCvtF2FSt scheduling class

Fixes the classification of VCVTPS2PHmr/VCVTPS2PHYmr which were tagged as WriteCvtF2FLd_WriteRMW (PR36887)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@330737 91177308-0d34-0410-b5e6-96231b3b80d8
14 files changed