[WATCHDOG] iTCO_wdt.c - pci_dev_put fix

for_each_pci_dev calls pci_get_device (and thus
it calls pci_dev_get). So we need to do a pci_dev_put
to keep the refcounting correct.
(Thanks to Jiri Slaby <jirislaby@gmail.com>)

Signed-off-by: Wim Van Sebroeck <wim@iguana.be>