ELF: Add missing case for AMDGPU to ELFFile::kindArch()

lib/ReaderWriter/ELF/ELFFile.cpp

template <class ELFT> Reference::KindArch ELFFile<ELFT>::kindArch() {
   case llvm::ELF::EM_ARM:
     return Reference::KindArch::ARM;
   case llvm::ELF::EM_HEXAGON:
     return Reference::KindArch::Hexagon;
   case llvm::ELF::EM_MIPS:
     return Reference::KindArch::Mips;
   case llvm::ELF::EM_AARCH64:
     return Reference::KindArch::AArch64;
+  case llvm::ELF::EM_AMDGPU:
+    return Reference::KindArch::AMDGPU;
   }
   llvm_unreachable("unsupported e_machine value");
 }
 
 template <class ELFT>
 std::error_code ELFFile<ELFT>::createAtomizableSections() {
   // Handle: SHT_REL and SHT_RELA sections:
   // Increment over the sections, when REL/RELA section types are found add