Fixes a bug in formation and simplification of an epilogue loop generated
during loop unroll of scf::ForOp (https://bugs.llvm.org/show_bug.cgi?id=46689)
Nit: consider using getTerminator() instead of back() for better readability.
Could you make it 11 iterations to make the test stronger (or an additional one if you prefer)? Is coverage missing for a symbolic upper bound in the presence of return values?