Merge Pull Request from: @zhengzengkai 
 
With the increase of memory capacity and density, the probability of
memory error increases. The increasing size and density of server RAM
in the data center and cloud have shown increased uncorrectable memory
errors.

Currently, the kernel has a mechanism to recover from hardware memory
errors. This patchset provides an new recovery mechanism.

For arm64, the hardware memory error handling is do_sea() which divided
into two cases:
 1. The user state consumed the memory errors, the solution is kill the
    user process and isolate the error page.
 2. The kernel state consumed the memory errors, the solution is panic.

For case 2, Undifferentiated panic maybe not the optimal choice, it can be
handled better, in some scenarios, we can avoid panic, such as uaccess, if
the uaccess fails due to memory error, only the user process will be affected,
kill the user process and isolate the user page with hardware memory errors
is a better choice. 
 
Link:https://gitee.com/openeuler/kernel/pulls/78 
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> 
Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>