mm: gmem: Introduce vm_object for gmem

euleros inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I7WLVX



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Introduce vm_object for gmem.

Co-developed-by: fangchuangchuang <fangchuangchuang@huawei.com>
Co-developed-by: Lemmy Huang <huangliming5@huawei.com>
Signed-off-by: Liu Chao <liuchao173@huawei.com>