JitBase: Make MergeAllowedNextInstructions a const member function

Source/Core/Core/PowerPC/JitCommon/JitBase.cpp

@@ -27,7 +27,7 @@ JitBase::JitBase() = default;
 
 JitBase::~JitBase() = default;
 
-bool JitBase::MergeAllowedNextInstructions(int count)
+bool JitBase::MergeAllowedNextInstructions(int count) const
 {
   if (CPU::GetState() == CPU::CPU_STEPPING || js.instructionsLeft < count)
     return false;

Source/Core/Core/PowerPC/JitCommon/JitBase.h

@@ -104,7 +104,7 @@ protected:
   PPCAnalyst::CodeBlock code_block;
   PPCAnalyst::PPCAnalyzer analyzer;
 
-  bool MergeAllowedNextInstructions(int count);
+  bool MergeAllowedNextInstructions(int count) const;
 
   void UpdateMemoryOptions();