README_HIP.md

适配HIP移植修改
```
1. cmake相关
    修改CMakeLists.txt，增加USE_HIP编译控制
    新增cmake/modules/ROCM.cmake，参考cmake/modules/CUDA.cmake进行编译配置
    增加CUDART_VERSION相关宏参数

2. 源码修改
添加宏判断，设备上不支持iostream
    src/array/selector.h:34

hip结构体hipPointerAttribute_t适配
    src/runtime/cuda/cuda_device_api.cc:251

添加显式基类限定词
    src/runtime/cuda/cuda_hashtable.cu:60
    src/runtime/cuda/cuda_hashtable.cu:104
    src/runtime/cuda/cuda_hashtable.cu:110

添加对CUDART_VERSION相关的条件判断flag
    src/array/cuda/spmm_hetero.cu:59
    src/array/cuda/spmm_hetero.cu:133

注释CUB_VERSION相关的static_assert检查
    src/array/cuda/rowwise_sampling_prob.cu:20

注释CUDART_VERSION相关的static_assert检查
    src/array/cuda/atomic.cuh:83

增加__HIPCC__宏定义的检查
    include/dgl/array_iterator.h:9









```