[compiler] Correctly initialize boolean value

This gets rid of a bunch of compiler warnings with MSVC.

Change-Id: I73440f0d203603fe39a2408d2b9cc647700aa5fc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1893334Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Michaël Zasso <mic.besace@gmail.com>
Cr-Commit-Position: refs/heads/master@{#64692}

src/compiler/backend/instruction.h

@@ -1419,7 +1419,7 @@ class V8_EXPORT_PRIVATE InstructionBlock final
   const RpoNumber loop_end_;
   int32_t code_start_;   // start index of arch-specific code.
   int32_t code_end_ = -1;     // end index of arch-specific code.
-  const bool deferred_ = -1;  // Block contains deferred code.
+  const bool deferred_;       // Block contains deferred code.
   const bool handler_;   // Block is a handler entry point.
   bool switch_target_ = false;
   bool alignment_ = false;  // insert alignment before this block