sw64: vdso: change vdso version

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I56P0Z



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Change vDSO version to LINUX_2.6 to improve compatibility with 3rd
party tools such as Linux Test Project(LTP).

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>