doesSectionRequireSymbols is meaningless on ELF, remove.

This is a nop. doesSectionRequireSymbols is only used from
isSymbolLinkerVisible. isSymbolLinkerVisible only use from ELF was in

if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined())
  return false;

if (Symbol.isTemporary())
  return false;

If the symbol is a temporary this code returns false and it is irrelevant if
we take the first if or not. If the symbol is not a temporary,
Asm.isSymbolLinkerVisible returns true without ever calling
doesSectionRequireSymbols.

This was an horrible leftover from when support for ELF was first added.

llvm-svn: 200894