sky2: reboot fix

The call to napi_disable() in the PCI shutdown handler is problematic,
and is aggravated by the new NAPI.
Also, make sure watchdog timer doesn't go off.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>