net/smc: add smcr_port_err() and smcr_link_down() processing

Call smcr_port_err() when an IB event reports an inactive IB device.
smcr_port_err() calls smcr_link_down() for all affected links.
smcr_link_down() either triggers the local DELETE_LINK processing, or
sends an DELETE_LINK LLC message to the SMC server to initiate the
processing.
The old handler function smc_port_terminate() is removed.
Add helper smcr_link_down_cond() to take a link down conditionally, and
smcr_link_down_cond_sched() to schedule the link_down processing to a
work.

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