iwlwifi: clarify config struct comments

It talks about treating different uCode APIs
as different pieces of hardware which really
isn't how we handle things.

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