net/smc: make wait for work request uninterruptible

Work requests are needed for every ib_post_send(), among them the
ib_post_send() to signal closing. If an smc socket program is cancelled,
the smc connections should be cleaned up, and require sending of closing
signals to the peer. This may fail, if a wait for
a free work request is needed, but is cancelled immediately due to the
cancel interrupt. To guarantee notification of the peer, the wait for
a work request is changed to uninterruptible.

And the area to receive work request completion info with
ib_poll_cq() is cleared first.
And _tx_ variable names are used in the _tx_routines for the
demultiplexing common type in the header.

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