iwlwifi: fix typo 'IWL_WATCHHDOG_DISABLED'

Commit 7c5ba4a8 ("iwlwifi: move queue
watchdog into transport") introduced the named constant
'IWL_WATCHHDOG_DISABLED'. Rename it to 'IWL_WATCHDOG_DISABLED'.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>