net/smc: handle ioctls SIOCINQ, SIOCOUTQ, and SIOCOUTQNSD

SIOCINQ returns the amount of unread data in the RMB.
SIOCOUTQ returns the amount of unsent or unacked sent data in the send
buffer.
SIOCOUTQNSD returns the amount of data prepared for sending, but
not yet sent.

Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>