net/smc: fix ethernet interface refcounting

If a pnet table entry is to be added mentioning a valid ethernet
interface, but an invalid infiniband or ISM device, the dev_put()
operation for the ethernet interface is called twice, resulting
in a negative refcount for the ethernet interface, which disables
removal of such a network interface.

This patch removes one of the dev_put() calls.

Fixes: 890a2cb4 ("net/smc: rework pnet table")
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>