iwlwifi: make IWLWIFI depend on CFG80211

Since IWLWIFI doesn't depend on MAC80211 anymore, it needs to depend
on CFG80211, because it uses a few symbols from it.  Add the
dependency on CFG80211 accordingly.

Additionally, make IWLWIFI_LEDS depend on IWLMVM or IWLDVM, since it
doesn't need mac80211 but must be used for these.

Fixes: aca432f0 ("iwlwifi: make MVM and DVM depend on MAC80211")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>