Fix "[turbofan] Spill rsi and rdi in their existing locations."

Commit 20f3a077 broke platforms using
embedded constant pools due to assumptions regarding stack frame
layout.

R=mtrofin@chromium.org, bmeurer@chromium.org, jarin@chromium.org, michael_dawson@ca.ibm.com
BUG=v8:4548
LOG=n

Review URL: https://codereview.chromium.org/1442273002

Cr-Commit-Position: refs/heads/master@{#31996}

src/compiler/frame.h

@@ -136,8 +136,8 @@ class Frame : public ZoneObject {
     return frame_slot_count_ - 1;
   }
 
-  static const int kContextSlot = 2;
-  static const int kJSFunctionSlot = 3;
+  static const int kContextSlot = 2 + StandardFrameConstants::kCPSlotCount;
+  static const int kJSFunctionSlot = 3 + StandardFrameConstants::kCPSlotCount;
 
  private:
   int AllocateAlignedFrameSlot(int width) {