[wasm] fix WASM test failures on big endian

WasmGraphBuilder::StoreMem is called with the last argument
as default with machine rep = kNode, which causes
BuildChangeEndiannessStore(val, memtype, type) to fail.

Originally added this fix in https://chromium-review.googlesource.com/633755
which got removed in this refactor https://chromium-review.googlesource.com/640591

R=clemensh@chromium.org, titzer@chromium.org, binji@chromium.org, jyan@ca.ibm.com
BUG=
LOG=N

Change-Id: I441e9b67517a31df780b35d2403c688d667b6789
Reviewed-on: https://chromium-review.googlesource.com/661097Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Jaideep Bajwa <bjaideep@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#47984}

src/compiler/wasm-compiler.h

@@ -287,7 +287,7 @@ class WasmGraphBuilder {
                 wasm::WasmCodePosition position);
   Node* StoreMem(MachineType memtype, Node* index, uint32_t offset,
                  uint32_t alignment, Node* val, wasm::WasmCodePosition position,
-                 wasm::ValueType type = wasm::kWasmStmt);
+                 wasm::ValueType type);
   static void PrintDebugName(Node* node);
 
   Node* Control() { return *control_; }

src/wasm/function-body-decoder.cc

@@ -311,7 +311,7 @@ class WasmGraphBuildingInterface {
                 const MemoryAccessOperand<true>& operand, const Value& index,
                 const Value& value) {
     BUILD(StoreMem, mem_type, index.node, operand.offset, operand.alignment,
-          value.node, decoder->position());
+          value.node, decoder->position(), type);
   }
 
   void CurrentMemoryPages(Decoder* decoder, Value* result) {