[x86] Simplify detection of jcxz/jecxz/jrcxz in disassembler.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225035 91177308-0d34-0410-b5e6-96231b3b80d8
[X86] Fix disassembly of absolute moves to work correctly in 16 and 32-bit modes with all 4 combinations of OpSize and AdSize prefixes being present or not.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225036 91177308-0d34-0410-b5e6-96231b3b80d8
[X86] Update disassembler tests for absolute move instructions to check the encodings. This provides testing for r225036. 64-bit mode is still broken.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225037 91177308-0d34-0410-b5e6-96231b3b80d8