tipc: fix sparse non static symbol warnings

Fixes the following sparse warnings:

net/tipc/socket.c:545:5: warning:
 symbol 'tipc_sk_proto_rcv' was not declared. Should it be static?
net/tipc/socket.c:2015:5: warning:
 symbol 'tipc_ioctl' was not declared. Should it be static?

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>