arm64: openeuler_defconfig: Enable ARM64_PMEM_LEGACY

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4O31I



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Enable legacy pmem register feature for arm64.

Signed-off-by: Zhuling <zhuling8@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>