LU-11133 dkms: Add missing ldiskfs module in dkms config

LU-11133 dkms: Add missing ldiskfs module in dkms config

The dkms.conf file generated by the script dkms.mkconf does not
include the ldiskfs kernel module. This results in not being able to
use ldiskfs when using the lustre-ldiskfs-dkms or lustre-all-dkms
packages.
This patch adds the module in the configuration for both of these
packages.

Test-Parameters: trivial
Signed-off-by: Sebastien Piechurski <sebastien.piechurski@atos.net>
Change-Id: Icc98fba208c78c3061fe591e3315af1eb9199f4f
Reviewed-on: https://review.whamcloud.com/32800
Reviewed-by: Nathaniel Clark <nclark@whamcloud.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>