iwlagn: leave notification waits on firmware errors

When the firmware encounters an error while the
driver is waiting for a notification, it will
never get that notification. Therefore, instead
of timing out, bail out on errors when waiting
for notifications.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>