fixing the compiling issue for the AMD architecture (#796)

Co-authored-by: Jeff Rasley <jerasley@microsoft.com>

op_builder/cpu_adam.py

@@ -36,7 +36,7 @@ class CPUAdamBuilder(CUDAOpBuilder):
                 return '-D__AVX512__'
             elif 'avx2' in result:
                 return '-D__AVX256__'
-        return ''
+        return '-D__SCALAR__'
 
     def cxx_args(self):
         CUDA_LIB64 = os.path.join(torch.utils.cpp_extension.CUDA_HOME, "lib64")