ksmbd: Constify struct ksmbd_transport_ops

'struct ksmbd_transport_ops' is not modified in these drivers.

Constifying this structure moves some data to a read-only section, so
increase overall security.

On a x86_64, with allmodconfig, as an example:
Before:
======
   text	   data	    bss	    dec	    hex	filename
  52184	   2085	    256	  54525	   d4fd	fs/smb/server/transport_rdma.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
  52260	   2021	    256	  54537	   d509	fs/smb/server/transport_rdma.o
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/server/connection.h

@@ -133,8 +133,8 @@ struct ksmbd_transport_ops {
 };
 
 struct ksmbd_transport {
-	struct ksmbd_conn		*conn;
-	struct ksmbd_transport_ops	*ops;
+	struct ksmbd_conn			*conn;
+	const struct ksmbd_transport_ops	*ops;
 };
 
 #define KSMBD_TCP_RECV_TIMEOUT	(7 * HZ)

fs/smb/server/transport_rdma.c

@@ -164,7 +164,7 @@ enum {
 	SMB_DIRECT_MSG_DATA_TRANSFER
 };
 
-static struct ksmbd_transport_ops ksmbd_smb_direct_transport_ops;
+static const struct ksmbd_transport_ops ksmbd_smb_direct_transport_ops;
 
 struct smb_direct_send_ctx {
 	struct list_head	msg_list;
@@ -2292,7 +2292,7 @@ bool ksmbd_rdma_capable_netdev(struct net_device *netdev)
 	return rdma_capable;
 }
 
-static struct ksmbd_transport_ops ksmbd_smb_direct_transport_ops = {
+static const struct ksmbd_transport_ops ksmbd_smb_direct_transport_ops = {
 	.prepare	= smb_direct_prepare,
 	.disconnect	= smb_direct_disconnect,
 	.shutdown	= smb_direct_shutdown,

fs/smb/server/transport_tcp.c

@@ -37,7 +37,7 @@ struct tcp_transport {
 	unsigned int			nr_iov;
 };
 
-static struct ksmbd_transport_ops ksmbd_tcp_transport_ops;
+static const struct ksmbd_transport_ops ksmbd_tcp_transport_ops;
 
 static void tcp_stop_kthread(struct task_struct *kthread);
 static struct interface *alloc_iface(char *ifname);
@@ -649,7 +649,7 @@ int ksmbd_tcp_set_interfaces(char *ifc_list, int ifc_list_sz)
 	return 0;
 }
 
-static struct ksmbd_transport_ops ksmbd_tcp_transport_ops = {
+static const struct ksmbd_transport_ops ksmbd_tcp_transport_ops = {
 	.read		= ksmbd_tcp_read,
 	.writev		= ksmbd_tcp_writev,
 	.disconnect	= ksmbd_tcp_disconnect,