vhost: add VHOST feature VHOST_BACKEND_F_BYTEMAPLOG

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



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Introduce new feature bit VHOST_BACKEND_F_BYTEMAPLOG for negotiating the
type of dirty pages.

As some hardware only support bytemap for logging, introduce a new
feature bit. When vhost device starte, negotiating dirty page type used
for logging.

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