[SCSI] mpt2sas: Before removing sas_device search device in list for _scsih_sas_device_remove

Fix a oops in _scsih_sas_device_remove.  The driver was attempting to
delete a object from the sas_device link list when the object was not
present.

Added sanity check for sas_device NULL dereference.
before deleting sas_device now driver will search device in list then
only it will follow device removal.
Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/mpt2sas/mpt2sas_scsih.c

@@ -537,10 +537,15 @@ _scsih_sas_device_remove(struct MPT2SAS_ADAPTER *ioc,
 {
 	unsigned long flags;
 
+	if (!sas_device)
+		return;
+
 	spin_lock_irqsave(&ioc->sas_device_lock, flags);
+	if (mpt2sas_scsih_sas_device_find_by_sas_address(ioc,
+	    sas_device->sas_address)) {
 		list_del(&sas_device->list);
-	memset(sas_device, 0, sizeof(struct _sas_device));
 		kfree(sas_device);
+	}
 	spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
 }