[turbofan] Use && instead of & in some condition.

R=jarin@chromium.org

Change-Id: I7005dc4c8282f8de75859f642e4d1808c6a8ef90
Reviewed-on: https://chromium-review.googlesource.com/c/1462000Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59487}

src/compiler/backend/code-generator.cc

@@ -147,7 +147,7 @@ void CodeGenerator::AssembleCode() {
   }
 
   // Check that {kJavaScriptCallCodeStartRegister} has been set correctly.
-  if (FLAG_debug_code & (info->code_kind() == Code::OPTIMIZED_FUNCTION ||
+  if (FLAG_debug_code && (info->code_kind() == Code::OPTIMIZED_FUNCTION ||
                           info->code_kind() == Code::BYTECODE_HANDLER)) {
     tasm()->RecordComment("-- Prologue: check code start register --");
     AssembleCodeStartRegisterCheck();