There is a tunable to select the fletcher 4 checksum implementation on
Linux but it was not present in FreeBSD.
Implement the sysctl handler for FreeBSD and use ZFS_MODULE_PARAM_CALL
to provide the tunable on both platforms.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes#11270
439dc034e9