Revert "[DAGCombiner] (add X, (adde Y, 0, Carry)) -> (adde X, Y, Carry)"

This reverts commit r294186.

On an internal test, this triggers an out-of-memory error on PPC,
presumably because there is another dagcombine that does the exact
opposite triggering and endless loop consuming more and more memory.

Chandler has started at creating a reduced test case and we'll attach it
as soon as possible.

llvm-svn: 294288