Kconfig: disable KTASK by default

hulk inclusion
category: bugfix
bugzilla: 46923
CVE: NA

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Enable KTASK in vfio, if the BAR size of some straight through
equipment device is too large, it will cause guest crash on booting.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>