smc: convert to ->poll_mask

smc->clcsock is an internal TCP socket, after TCP socket
converts to ->poll_mask, ->poll doesn't exist any more.
So just convert smc socket to ->poll_mask too.

Fixes: 2c7d3dac ("net/tcp: convert to ->poll_mask")
Reported-by:  <syzbot+f5066e369b2d5fff630f@syzkaller.appspotmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>