sw64: add missing pkey syscall numbers

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



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Most architectures define system call numbers for the pkey system calls
even when they don't support the features, and perhaps never will. sw64
miss these before, so just define them anyway for consistency.

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>