scsi: cxlflash: Cache owning adapter within context

The context removal routine requires access to the owning adapter
structure to reset the context within the AFU as part of the tear down
sequence. In order to support kref adoption, the owning adapter must be
accessible from the release handler. As the kref framework only provides
the kref reference as the sole parameter, another means is needed to
derive the owning adapter.

As a remedy, the owning adapter reference is saved off within the
context during initialization.

Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Acked-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>