iwlwifi: tracing: add rx cmd header fields

Having explicit rx cmd header fields is useful, as it can
be used for event filtering (e.g. saving only debug logs,
rather than the whole data)

Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>