net: tg3: fix NULL pointer dereference in tg3_io_error_detected and tg3_io_slot_reset

Commit d8af4dfd

 ("net/tg3: Fix kernel crash") introduced a possible
NULL pointer dereference in tg3 driver when !netdev || !netif_running(netdev)
condition is met and netdev is NULL. Then, the jump to the 'done' label
calls dev_close() with a netdevice that is NULL. Therefore, only call
dev_close() when we have a netdevice, but one that is not running.

[ Add the same checks in tg3_io_slot_reset() per Gavin Shan - by Nithin
Nayak Sujir ]

Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Gavin Shan <shangw@linux.vnet.ibm.com>
Cc: Michael Chan <mchan@broadcom.com>
Signed-off-by: Nithin Nayak Sujir <nsujir@broadcom.com>
Signed-off-by: Nithin Nayak Sujir <nsujir@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>