sw64: optimize simd version of memcpy and memset

Sunway inclusion
category: performance
bugzilla: https://gitee.com/openeuler/kernel/issues/I56XPR



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Optimize the use of memb instruction in memset.

Rewrite memcpy and use simd instruction to copy data when src and dest
are not co-aligned.

When data size is larger than 2KB, use _nc store instruction to improve
performance.

Signed-off-by: Mao Minkai <maominkai@wxiat.com>

Signed-off-by: Gu Zitao <guzitao@wxiat.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>