treewide: cleanup code

- Remove some unused data fields
- Fix a few typos in comments, etc

[cleanup commit message]
Signed-off-by: Nick Hainke <vincent@systemli.org>

src/utils/ieee80211_utils.c

@@ -8,6 +8,7 @@ double iee80211_calculate_expected_throughput_mbit(int exp_thr) {
     return (((double) exp_thr) / 1000);
 }
 
+// FIXME: This calculation seems to be unreliable.  Is it device specific?
 int rcpi_to_rssi(int rcpi)
 {
     return rcpi / 2 - 110;