zdb: fix printf() length for uint64_t devid

Bug introduced in 213d6829673.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Warner Losh <imp@FreeBSD.org>
Signed-off-by: Martin Matuska <mm@FreeBSD.org>
Closes #15606