Revert 53729, after waking up in the middle of

Revert 53729, after waking up in the middle of
the night realising that it was wrong :)  I
think the reason the same type was being used
for the shufflevec of indices as for the actual
indices is so that if one of them needs splitting
then so does the other.  After my patch it might
be that the indices need splitting but not the
rest, yet there is no good way of handling that.
I think the right solution is to not have the
shufflevec be an operand at all: just have it
be the list of numbers it actually is, stored
as extra info in the node.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53768 91177308-0d34-0410-b5e6-96231b3b80d8