imsm: fix first volume autolayout with IMSM_NO_PLATFORM

imsm: fix first volume autolayout with IMSM_NO_PLATFORM

Autolayout_imsm() is not executed if IMSM_NO_PLATFORM=1 is set.
This causes that first volume cannot be created. Disk for new volume are
never configured.

Fix it by making autolayout_imsm() independent from super->orom because
NULL there means that IMSM_NO_PLATFORM=1 is set. There are not platform
restrictions to create volume, we just analyze drives. It is safe.

Fixes: 6d4d9ab295de ("imsm: use same slot across container")
Signed-off-by: Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>