Change IR generation for SRST, CLST, and CLCLE to not generate cc=3.

Change IR generation for SRST, CLST, and CLCLE to not generate cc=3.
Two reasons:
(1) Consistency in implementation (we don't generate cc=3 for "translate",
   "convert to unicode" and possibly other insns)
(2) There is nothing to be gained. A program that does not handle cc=3
    correctly (by looping back to the insn that generated it) may exhibit
    unpredictable behaviours. And there is no way for us to match that (as
    we cannot know when hardware decides to interrupt the insn). So why
    add complexity for that.

git-svn-id: svn://svn.valgrind.org/vex/trunk@2446