LoongArch: Export some arch-specific pm interfaces

mainline inclusion
from mainline-v6.5-rc1
commit 31f1a8b0
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7MWTU


CVE: NA

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Some PMC (Power Management Controllers) need to support DTS and will use
the suspend interfaces thus this patch was to export such interfaces for
their use.

Signed-off-by: Yongzhen Zhang <zhangyongzhen@kylinos.cn>
Signed-off-by: Yinbo Zhu <zhuyinbo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>