iwlwifi: mvm: minor cleanups to HE radiotap code

Remove a stray empty line, unbreak some lines that aren't
really that long, and move on variable setting into the
initializer to avoid initializing it twice.

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