RDS: TCP: Fix non static symbol warnings

Fixes the following sparse warnings:

net/rds/tcp.c:59:5: warning:
 symbol 'rds_tcp_min_sndbuf' was not declared. Should it be static?
net/rds/tcp.c:60:5: warning:
 symbol 'rds_tcp_min_rcvbuf' was not declared. Should it be static?
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: NSowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: NSantosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/rds/tcp.c

@@ -57,8 +57,8 @@ static int rds_tcp_skbuf_handler(struct ctl_table *ctl, int write,
 				 void __user *buffer, size_t *lenp,
 				 loff_t *fpos);
 
-int rds_tcp_min_sndbuf = SOCK_MIN_SNDBUF;
-int rds_tcp_min_rcvbuf = SOCK_MIN_RCVBUF;
+static int rds_tcp_min_sndbuf = SOCK_MIN_SNDBUF;
+static int rds_tcp_min_rcvbuf = SOCK_MIN_RCVBUF;
 
 static struct ctl_table rds_tcp_sysctl_table[] = {
 #define	RDS_TCP_SNDBUF	0