MCSectionGOFF: Remove classof

The object file format specific derived classes are used in context like
MCStreamer and MCObjectTargetWriter where the type is statically known.
We don't use isa/dyn_cast and we want to eliminate
MCSection::SectionVariant in the base class.

Author: MaskRay

llvm/include/llvm/MC/MCSectionGOFF.h

@@ -123,8 +123,6 @@ class LLVM_ABI MCSectionGOFF final : public MCSection {
   bool requiresNonZeroLength() const { return RequiresNonZeroLength; }
 
   void setName(StringRef SectionName) { Name = SectionName; }
-
-  static bool classof(const MCSection *S) { return S->getVariant() == SV_GOFF; }
 };
 } // end namespace llvm
 

llvm/lib/MC/GOFFObjectWriter.cpp

@@ -336,7 +336,7 @@ void GOFFWriter::defineSymbols() {
   unsigned Ordinal = 0;
   // Process all sections.
   for (MCSection &S : Asm) {
-    auto &Section = cast<MCSectionGOFF>(S);
+    auto &Section = static_cast<MCSectionGOFF &>(S);
     Section.setOrdinal(++Ordinal);
     defineSectionSymbols(Section);
   }