Update documentation for new parameter "zfs_qat_disable"

Update documentation in zfs-module-parameters.5 for new
parameter "zfs_qat_disable" which was introduced by #5846.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Weigang Li <weigang.li@intel.com>
Closes #5914