Hexagon: Change insn class to support instruction encoding.
This patch doesn't introduce any functionality changes.
It adds some new fields to the Hexagon instruction classes and
changes their layout to support instruction encoding.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175205 91177308-0d34-0410-b5e6-96231b3b80d8