scsi: cxlflash: Remove adapter file descriptor cache

The adapter file descriptor was previously cached within the kernel for
a given context in order to support performing a close on behalf of an
application. This is no longer needed as applications are now required
to perform a close on the adapter file descriptor.

Inspired-by: Al Viro <viro@zeniv.linux.org.uk>
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>