Rename HasData to IsRegistered.

There is no MCSectionData, so the old name is now meaningless.

Also remove some asserts/checks that were there just because the information
they used was in MCSectionData.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238708 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCAssembler.h

@@ -911,11 +911,11 @@ public:
   }
 
   void registerSymbol(const MCSymbol &Symbol, bool *Created = nullptr) {
-    bool New = !Symbol.hasData();
+    bool New = !Symbol.isRegistered();
     if (Created)
       *Created = New;
     if (New) {
-      Symbol.initializeData();
+      Symbol.setIsRegistered(true);
       Symbols.push_back(&Symbol);
     }
   }