Revert "[WebAssembly] Split and recombine multivalue calls for ISel"
This reverts commit 28857d14a86b1e99a9d2795636a5faf17674f5a2. This
commit worked toward a solution that did not turn out to be feasible
because MachineInstrs cannot contain an arbitrary number of defs.
Subscribers: dschuff, sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits
Differential Revision: https://reviews.llvm.org/D73927