Fix zio_flag_t print format
Follow up for 4938d01d which changed zio_flag from enum to uint64_t.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Signed-off-by: Youzhong Yang <yyang@mathworks.com>
Closes #14100