DSPEmitter: Make FlagsNeeded() a const member function

This doesn't modify any class data.

Source/Core/Core/DSP/Jit/DSPEmitter.cpp

@@ -90,7 +90,7 @@ void DSPEmitter::checkExceptions(u32 retval)
   SetJumpTarget(skipCheck);
 }
 
-bool DSPEmitter::FlagsNeeded()
+bool DSPEmitter::FlagsNeeded() const
 {
   const u8 flags = DSPAnalyzer::GetCodeFlags(compilePC);
 

Source/Core/Core/DSP/Jit/DSPEmitter.h

@@ -34,7 +34,7 @@ public:
   Block CompileStub();
   void Compile(u16 start_addr);
 
-  bool FlagsNeeded();
+  bool FlagsNeeded() const;
 
   void FallBackToInterpreter(UDSPInstruction inst);