Fix gcc build after de3a485 due to a gcc bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92598

This should fix gcc based builders such as http://lab.llvm.org:8011/#/builders/76/builds/1683

Author: dyung

llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp

@@ -83,7 +83,7 @@ using namespace llvm::XCOFF;
 // This specialization is needed here because that type is used as keys in the
 // map representing TOC entries.
 template <>
-struct DenseMapInfo<std::pair<const MCSymbol *, MCSymbolRefExpr::VariantKind>> {
+struct llvm::DenseMapInfo<std::pair<const MCSymbol *, MCSymbolRefExpr::VariantKind>> {
   using TOCKey = std::pair<const MCSymbol *, MCSymbolRefExpr::VariantKind>;
 
   static inline TOCKey getEmptyKey() {