Document ZFS_DKMS_ENABLE_DEBUGINFO in userland configuration
Document the ZFS_DKMS_ENABLE_DEBUGINFO option in the userland
configuration file, as done with the other ZFS_DKMS_* options.
It has been introduced with commit e45c1734a665 ("dkms: Enable
debuginfo option to be set with zfs sysconfig file") but isn't
mentioned anywhere other than the 'dkms.conf' file (generated).
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
Closes #9191