Add a kWithoutReadBarrier in GetSavedEntryPointOfPreCompiledMethod.

To conform to the newly added ScopedDebugDisallowReadBarriers. This is
only a problem when booting JIT zygote in debug builds.

Test: test.py
Change-Id: I1487400583185c18a965fc12a9e79919bbf9f0d5
diff --git a/runtime/jit/jit_code_cache.cc b/runtime/jit/jit_code_cache.cc
index 4271a09..c1488ca 100644
--- a/runtime/jit/jit_code_cache.cc
+++ b/runtime/jit/jit_code_cache.cc
@@ -335,7 +335,7 @@
   ScopedDebugDisallowReadBarriers sddrb(self);
   if (method->IsPreCompiled()) {
     const void* code_ptr = nullptr;
-    if (method->GetDeclaringClass()->IsBootStrapClassLoaded()) {
+    if (method->GetDeclaringClass<kWithoutReadBarrier>()->IsBootStrapClassLoaded()) {
       code_ptr = zygote_map_.GetCodeFor(method);
     } else {
       MutexLock mu(self, *Locks::jit_lock_);