Fix the type of the raidz_outlier_check_interval_ms parameter

It's an hrtime_t, which is an unsigned long long. In practice this is
just a U64.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Allan Jude <allan@klarasystems.com>
Reviewed-by: Rob Norris <rob.norris@klarasystems.com>
Signed-off-by: Mark Johnston <markj@FreeBSD.org>
Closes #17833