scsi: qla2xxx: Fix potential NULL pointer dereference

commit 464ea494 upstream.

Klocwork tool reported 'cur_dsd' may be dereferenced.  Add fix to validate
pointer before dereferencing the pointer.

Cc: stable@vger.kernel.org
Signed-off-by: Bikash Hazarika <bhazarika@marvell.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Link: https://lore.kernel.org/r/20230607113843.37185-3-njavali@marvell.com


Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>