kernel: iscsi-initator: fix kernel config symbols

kernel: iscsi-initator: fix kernel config symbols

Enable SCSI low-level drivers on targets that don't have it already in
order to fix following build failures on few platforms:

  .config:4739:warning: symbol value 'm' invalid for SCSI_LOWLEVEL
 * Restart config...
 * SCSI low-level drivers
 SCSI low-level drivers (SCSI_LOWLEVEL) [Y/n] (NEW) aborted!

Fixes: b88f8202c4ce ("kernel: add iscsi-initator support")
Signed-off-by: Lucian Cristian <lucian.cristian@gmail.com>
[commit subject and description facelift]
Signed-off-by: Petr Štetiar <ynezz@true.cz>