mm/sharepool: Delete redundant size and alloc_size in sp_meminfo.

hulk inclusion
category: other
bugzilla: https://gitee.com/openeuler/kernel/issues/I6ET9W



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alloc_size can be obtained by adding alloc_nsize to alloc_hsize,
and size can be obtained by adding alloc_nsize to alloc_hsize and
k2u_size. Therefore, alloc_size and size are redundant
and can be deleted.

Signed-off-by: Xu Qiang <xuqiang36@huawei.com>