net/smc: rework pnet table to support SMC-R failover

The pnet table stored pnet ids in the smc device structures. When a
device is going down its smc device structure is freed, and when the
device is brought online again it no longer has a pnet id set.
Rework the pnet table implementation to store the device name with their
assigned pnet id and apply the pnet id to devices when they are
registered.

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>