S390:[wasm-simd] fix I64x2Mul codegen on s390

Change-Id: I24627a0fafbafa370877a3794fe2d1e40f11f622
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2427384Reviewed-by: Junliang Yan <junyan@redhat.com>
Commit-Queue: Milad Farazmand <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/master@{#70101}

src/compiler/backend/s390/code-generator-s390.cc

@@ -3280,8 +3280,8 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       Register scratch_0 = r0;
       Register scratch_1 = r1;
       for (int i = 0; i < 2; i++) {
-        __ vlgv(scratch_0, src0, MemOperand(r0, 0), Condition(3));
-        __ vlgv(scratch_1, src1, MemOperand(r0, 0), Condition(3));
+        __ vlgv(scratch_0, src0, MemOperand(r0, i), Condition(3));
+        __ vlgv(scratch_1, src1, MemOperand(r0, i), Condition(3));
         __ Mul64(scratch_0, scratch_1);
         scratch_0 = r1;
         scratch_1 = ip;