SUNRPC: Define xs_tcp_fin_timeout only if CONFIG_SUNRPC_DEBUG

Now that the linger code is gone, the xs_tcp_fin_timeout variable has
no real function. Keep it for now, since it is part of the /proc
interface, but only define it if that /proc interface is enabled.
Suggested-by: NAnna Schumaker <Anna.Schumaker@netapp.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

net/sunrpc/xprtsock.c

@@ -63,6 +63,8 @@ static unsigned int xprt_max_tcp_slot_table_entries = RPC_MAX_SLOT_TABLE;
 static unsigned int xprt_min_resvport = RPC_DEF_MIN_RESVPORT;
 static unsigned int xprt_max_resvport = RPC_DEF_MAX_RESVPORT;
 
+#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
+
 #define XS_TCP_LINGER_TO	(15U * HZ)
 static unsigned int xs_tcp_fin_timeout __read_mostly = XS_TCP_LINGER_TO;
 
@@ -75,8 +77,6 @@ static unsigned int xs_tcp_fin_timeout __read_mostly = XS_TCP_LINGER_TO;
  * someone else's file names!
  */
 
-#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
-
 static unsigned int min_slot_table_size = RPC_MIN_SLOT_TABLE;
 static unsigned int max_slot_table_size = RPC_MAX_SLOT_TABLE;
 static unsigned int max_tcp_slot_table_limit = RPC_MAX_SLOT_TABLE_LIMIT;