[X86] Merge hasVEX_i8ImmReg into the ImmFormat type which had extra unused encodings. This saves one bit in TSFlags. NFC

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279412 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed