kconfig: Add script to check & update openeuler_defconfig

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8J6X4
CVE: NA

Reference: https://gitee.com/openeuler/kernel/pulls/286



-----------------------------------------

If new options are introduced, but openeuler_defconfig is not explicitly
configured, the actual compiled version may be configured according to
the default settings, which may be different from the author's expectation.
Therefore, some commands/scripts are added to help developers to check and
update the defconfig. It is also convenient for continuous integration tools to
check the consistency of defconfig.

```
Usage:
  make check_oedefconfig
  #
  # New options might needs to be updated to the default configuration
  # file. Use the following command:
  # 'make openeuler_defconfig/menuconfig/update_oedefconfig/save_oedefconfig'
  # !!! DO NOT EDIT !!!
  #
  # defconfig: arch/arm64/configs/openeuler_defconfig
  #
  CONFIG_MEMCG=n
  CONFIG_BLK_CGROUP=n
  CONFIG_CFS_BANDWIDTH=n
  CONFIG_RT_GROUP_SCHED=n
  CONFIG_CGROUP_PIDS=n
  CONFIG_CGROUP_RDMA=n
  CONFIG_CGROUP_FREEZER=n
  CONFIG_CGROUP_HUGETLB=n
  CONFIG_CPUSETS=n

  make update_oedefconfig
  # Update openeuler_defconfig base on current source code

  make save_oedefconfig
  # Save current .config to openeuler_defconfig'
```

If someone adds a new Kconfig, he should also explicitly update
openeuler_defconfig, whether it's enabled or disabled.

Again, do *NOT* edit openeuler_defconfig directly.

Signed-off-by: Liu Chao <liuchao173@huawei.com>
Cc: Jason Zeng <jason.zeng@intel.com>
Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Conflicts:
	scripts/kconfig/Makefile
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>