[wasm][mv] Fix multi-return validation order

R=ahaas@chromium.org

Bug: v8:10328
Change-Id: I19ecad9161ea61b4c8a22f80f8ac10ebf23dee53
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2148783
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67127}

src/wasm/function-body-decoder-impl.h

@@ -2063,7 +2063,7 @@ class WasmFullDecoder : public WasmDecoder<validate> {
             // Since we deal with unreachable code, we do not have to keep the
             // values.
             int num_returns = static_cast<int>(this->sig_->return_count());
-            for (int i = 0; i < num_returns; ++i) {
+            for (int i = num_returns - 1; i >= 0; --i) {
               Pop(i, this->sig_->GetReturn(i));
             }
           }