[TableGen] Replace instructions() with getInstructionsByEnumValue(). No need to make an iterator_range when we already have a function that returns an ArrayRef. NFC

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@258019 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed