virt: acrn: using for_each_set_bit to simplify the code

It's more cleanly to use for_each_set_bit() instead of opencoding it.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Fei Li <fei1.li@intel.com>
Link: https://lore.kernel.org/r/20220704125044.2192381-1-yangyingliang@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>