vdpa: add log operations

virt inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I86ITO



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Several new interfaces are introduced to allow vdpa
device logging guest memory during live migration and
return to the VMM.

The set_log_base interface is used to set the base
address for buffer storing bitmaps.

The set_log_size interface is used to set the size
of buffer used for storing bitmaps.

The log_sync interface is used to copy the bitmaps
from kernel space to user space of VMM.

These operations are optional. If they are not implemented,
these operations will return EOPNOTSUPP.

Signed-off-by: jiangdongxu <jiangdongxu1@huawei.com>