KVM: x86: Do not write protect huge page in initially-all-set mode

Currently, when dirty logging is started in initially-all-set mode,
we write protect huge pages to prepare for splitting them into
4K pages, and leave normal pages untouched as the logging will
be enabled lazily as dirty bits are cleared.

However, enabling dirty logging lazily is also feasible for huge pages.
This not only reduces the time of start dirty logging, but it also
greatly reduces side-effect on guest when there is high dirty rate.

Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Message-Id: <20210429034115.35560-3-zhukeqian1@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>