Missing modules for scsi cdrom config_drive in ppc64le

config_drive cannot be enabled since it uses scsi cdrom device on /dev/sr0 for Power platform.

The missing modules, as far I could check are the following: scsi_mod, como sr_mod, sg_mod, cdrom and ibmvscsi.

Any test in Tempest suite that attempts to verify config_drive will fail:
264 # Verify metadata on config drive
265 if CONF.compute_feature_enabled.config_drive:
266 cmd_blkid = 'blkid -t LABEL=config-2 -o device'

—— qemu console ——

Populating /vdevice/v-scsi@2000
       SCSI: Looking for devices
          8000000000000000 CD-ROM : "QEMU QEMU CD-ROM 2.5+"

—— libvirt ——

    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw' cache='none'/>
      <source file='/opt/stack/data/nova/instances/d96f06dd-99be-4ad1-81b8-fa24b249792b/disk.config'/>
      <backingStore/>
      <target dev='sda' bus='scsi'/>
      <readonly/>
      <alias name='scsi0-0-0-0'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>

-— cirros ——

$ dmesg | grep SCSI
[ 0.101770] SCSI subsystem initialized
[ 0.292384] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 246)

$ cat /etc/modules
# modules here are loaded one per line
ibmvscsic # arch=powerpc
ibmveth # arch=powerpc
virtio_scsi
virtio_pci
virtio_blk
virtio_net
e1000
ne2k-pci # arch=x86
8139cp # arch=x86
pcnet32 # arch=x86
ip_tables
isofs
vfat
nls_cp437
nls_iso8859-1

$ ls /dev/sd*
ls: /dev/sd*: No such file or directory

$ ls /dev/sr*
ls: /dev/sr*: No such file or directory