net/smc: return 0 for ioctl calls in states INIT and CLOSED

A connected SMC-socket contains addresses of descriptors for the
send buffer and the rmb (receive buffer). Fields of these descriptors
are used to determine the answer for certain ioctl requests.
Add extra handling for unconnected SMC socket states without valid
buffer descriptor addresses.

Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Reported-by:  <syzbot+e6714328fda813fc670f@syzkaller.appspotmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>