net/smc: move sock lock in smc_ioctl()

When an SMC socket is connecting it is decided whether fallback to
TCP is needed. To avoid races between connect and ioctl move the
sock lock before the use_fallback check.

Reported-by:  <syzbot+5b2cece1a8ecb2ca77d8@syzkaller.appspotmail.com>
Reported-by:  <syzbot+19557374321ca3710990@syzkaller.appspotmail.com>
Fixes: 1992d998 ("net/smc: take sock lock in smc_ioctl()")
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>