forked from Mirrors/opensbi

The original version of ctz will cause an endless loop, if the parameter passed in is 0. This commit fixes this bug. Signed-off-by: Xiang W <wxjstz@126.com> Reviewed-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Anup Patel <anup.patel@wdc.com>