[Clang] Move AMDGPU IAS enabling to Generic_GCC::IsIntegratedAssemblerDefault, NFC

[brad]

Summary

Move enabling of IAS back to Generic_GCC::IsIntegratedAssemblerDefault().

clang/lib/Driver/ToolChains/AMDGPU.h

StringRef getOptionDefault(options::ID OptID) const {
     assert(opt != OptionsDefault.end() && "No Default for Option");
     return opt->second;
   }
 
 public:
   AMDGPUToolChain(const Driver &D, const llvm::Triple &Triple,
                   const llvm::opt::ArgList &Args);
   unsigned GetDefaultDwarfVersion() const override { return 5; }
-  bool IsIntegratedAssemblerDefault() const override { return true; }
-  bool IsMathErrnoDefault() const override { return false; }
 
-  bool useIntegratedAs() const override { return true; }
+  bool IsMathErrnoDefault() const override { return false; }
   bool isCrossCompiling() const override { return true; }
   bool isPICDefault() const override { return false; }
   bool isPIEDefault(const llvm::opt::ArgList &Args) const override {
     return false;
   }
   bool isPICDefaultForced() const override { return false; }
   bool SupportsProfiling() const override { return false; }
 

clang/lib/Driver/ToolChains/Gnu.cpp

 bool Generic_GCC::isPICDefaultForced() const {
   return getArch() == llvm::Triple::x86_64 && getTriple().isOSWindows();
 }
 
 bool Generic_GCC::IsIntegratedAssemblerDefault() const {
   switch (getTriple().getArch()) {
   case llvm::Triple::aarch64:
   case llvm::Triple::aarch64_be:
+  case llvm::Triple::amdgcn:
   case llvm::Triple::arm:
   case llvm::Triple::armeb:
   case llvm::Triple::avr:
   case llvm::Triple::bpfel:
   case llvm::Triple::bpfeb:
   case llvm::Triple::csky:
   case llvm::Triple::hexagon:
   case llvm::Triple::lanai:
   case llvm::Triple::loongarch32:
   case llvm::Triple::loongarch64:
   case llvm::Triple::m68k:
   case llvm::Triple::mips:
   case llvm::Triple::mipsel:
   case llvm::Triple::mips64:
   case llvm::Triple::mips64el:
   case llvm::Triple::msp430:
   case llvm::Triple::ppc:
   case llvm::Triple::ppcle:
   case llvm::Triple::ppc64:
   case llvm::Triple::ppc64le:
+  case llvm::Triple::r600:
   case llvm::Triple::riscv32:
   case llvm::Triple::riscv64:
   case llvm::Triple::sparc:
   case llvm::Triple::sparcel:
   case llvm::Triple::sparcv9:
   case llvm::Triple::systemz:
   case llvm::Triple::thumb:
   case llvm::Triple::thumbeb: