REGRESSION (r210244): Release JSC Stress test failure: wasm.yaml/wasm/js-api/wasm...

REGRESSION (r210244): Release JSC Stress test failure: wasm.yaml/wasm/js-api/wasm-to-wasm.js.default-wasm
https://bugs.webkit.org/show_bug.cgi?id=166669
<rdar://problem/29856455>

Reviewed by Saam Barati.

Bug #165282 added wasm -> wasm calls, but caused crashes in
release builds because the pinned registers are also callee-saved
and were being clobbered. B3 didn't see itself clobbering them
when no memory was used, and therefore omitted a restore.

This was causing the C++ code in callWebAssemblyFunction to crash
because $r12 was 0, and it expected it to have its value prior to
the call.

* wasm/WasmB3IRGenerator.cpp:
(JSC::Wasm::createJSToWasmWrapper):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@210259 268f45cc-cd09-0410-ab3c-d52691b4dbfc