Remove unnecessary classof()'s

isa<> et al. automatically infer when the cast is an upcast (including a
self-cast), so these are no longer necessary.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165767 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCSection.h

@@ -64,8 +64,6 @@ namespace llvm {
     /// isVirtualSection - Check whether this section is "virtual", that is
     /// has no actual object file contents.
     virtual bool isVirtualSection() const = 0;
-
-    static bool classof(const MCSection *) { return true; }
   };
 
 } // end namespace llvm