FreeBSD does not have the free command. This command is only used by
Linux in a perf hostinfo function.
Move free from the list of common commands to the list of Linux
commands.
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes#10011