net/smc: add smcd support to the pnet table

Currently, users can only set pnetids for netdevs and ib devices in the
pnet table. This patch adds support for smcd devices to the pnet table.

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