iwlwifi: tracing: decouple from mac80211

In order to be able to properly record SKBs that didn't come through
mac80211, don't rely on the IEEE80211_TX_CTRL_PORT_CTRL_PROTO flag
but instead check for ETH_P_PAE directly.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>