[MLIR] Handle in-place folding properly in greedy pattern rewrite driver

OperatioFolder::tryToFold performs both true folding and in a few
instances in-place updates through op rewrites. In the latter case, we
should still be applying the supplied pattern rewrites in the same
iteration; however this wasn't the case since tryToFold returned
success() for both true folding and in-place updates, and the patterns
for the in-place updated ops were being applied only in the next
iteration of the driver's outer loop. This fix would make it converge
faster.

Differential Revision: https://reviews.llvm.org/D77485