LoongArch: Add VDSO and VSYSCALL support

mainline inclusion
from mainline-v5.19-rc1
commit c6b99bed
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5OHOB


CVE: NA

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Add VDSO and VSYSCALL support (sigreturn, gettimeofday and its friends)
for LoongArch.

Reviewed-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>