DSPIntExtOps: Make IsSameMemArea internally linked

inline has external linkage, which doesn't really make sense here, given
the function is only used within this translation unit. So we can
replace inline with static.

While we're at it, the code within the function can also be compressed
to a single return statement.

Source/Core/Core/DSP/Interpreter/DSPIntExtOps.cpp

@@ -34,13 +34,10 @@ namespace Interpreter
 {
 namespace Ext
 {
-inline bool IsSameMemArea(u16 a, u16 b)
+static bool IsSameMemArea(u16 a, u16 b)
 {
   // LM: tested on Wii
-  if ((a >> 10) == (b >> 10))
-    return true;
-  else
-    return false;
+  return (a >> 10) == (b >> 10);
 }
 
 // DR $arR