x64Emitter: Move FloatOp and NormalOp enums to the cpp file

These are only used internally. This also allows us to eliminate some
symbols that get dumped into the exposed Gen namespace.

By extension this also hides the Write[X] functions from OpArg's public
interface. This is only used internally by XEmitter, so they shouldn't
be usable by anything else.

Source/Core/Common/x64Emitter.cpp

@@ -76,6 +76,32 @@ enum NormalSSEOps
   sseMOVNTP = 0x2B,
 };
 
+enum NormalOp : int
+{
+  nrmADD,
+  nrmADC,
+  nrmSUB,
+  nrmSBB,
+  nrmAND,
+  nrmOR,
+  nrmXOR,
+  nrmMOV,
+  nrmTEST,
+  nrmCMP,
+  nrmXCHG,
+};
+
+enum FloatOp : int
+{
+  floatLD = 0,
+  floatST = 2,
+  floatSTP = 3,
+  floatLD80 = 5,
+  floatSTP80 = 7,
+
+  floatINVALID = -1,
+};
+
 void XEmitter::SetCodePtr(u8* ptr)
 {
   code = ptr;