scsi: cxlflash: Adapter context support for OCXL

Add support to create and release the adapter contexts for OCXL and provide
means to specify certain contexts as a master.

The existing cxlflash core has a design requirement that each host will have a
single host context available by default. To satisfy this requirement, one
host adapter context is created when the hardware AFU is initialized. This is
returned by the get_context() fop.

Signed-off-by: Uma Krishnan <ukrishn@linux.vnet.ibm.com>
Acked-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Reviewed-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>