sw64: switch GUP to the generic get_user_pages_fast() implementation

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I56U83



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sw64 fits all conditions required by the generic get_user_pages_fast()
code, so activate this feature by default.

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>