mm/swap_slots: fix out-of-bounds access of percpu area

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8LKYV



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Variable swp_type_slots is an array with type 'struct swap_slots_cache[]'.
So raw_cpu_ptr(&swp_type_slots) is correspoinding pointer of array. Its
type is 'struct swap_slots_cache[]' rather than 'struct swap_slots_cache'.
So the offset of raw_cpu_ptr(&swp_type_slots)[swap_type] is out-of-bounds.
Use raw_cpu_ptr(&swp_type_slots[swap_type]) to get the correct variable.

Fixes: 8e41c366 ("mm: swap_slots: add per-type slot cache")
Signed-off-by: Liu Shixin <liushixin2@huawei.com>