sw64: clean up a.out and ECOFF binary related headers

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I56OLG



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It never support a.out and ECOFF binaries on sw64 systems, and the
related headers can be removed.

The user.h is only used for a.out files, and we use generic version
instead.

Signed-off-by: He Sheng <hesheng@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>