mm: add do_vm_mmap

ascend inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4D63I


CVE: NA

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An interface do_vm_mmap is added to support the allocation in
the address spaces of other processes.

Signed-off-by: Fang Lijun <fanglijun3@huawei.com>
Signed-off-by: Zhou Guanghui <zhouguanghui1@huawei.com>
Reviewed-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>