[x86] eliminate unnecessary shuffling/moves with unary scalar math ops (PR21507)

Finish the job that was abandoned in D6958 following the refactoring in
http://reviews.llvm.org/rL230221:

1. Uncomment the intrinsic def for the AVX r_Int instruction.
2. Add missing r_Int entries to the load folding tables; there are already
   tests that check these in "test/Codegen/X86/fold-load-unops.ll", so I
   haven't added any more in this patch.
3. Add patterns to solve PR21507 ( https://llvm.org/bugs/show_bug.cgi?id=21507 ).

So instead of this:

  movaps	%xmm0, %xmm1
  rcpss	%xmm1, %xmm1
  movss	%xmm1, %xmm0

We should now get:

  rcpss	%xmm0, %xmm0

And instead of this:

  vsqrtss	%xmm0, %xmm0, %xmm1
  vblendps	$1, %xmm1, %xmm0, %xmm0 ## xmm0 = xmm1[0],xmm0[1,2,3]

We should now get:

  vsqrtss	%xmm0, %xmm0, %xmm0


Differential Revision: http://reviews.llvm.org/D9504

llvm-svn: 236740