Airtime - calculate ms in a hour in preprocessor

src/airtime.h

@@ -28,6 +28,9 @@
 #define SECONDS_PER_PERIOD 3600
 #define PERIODS_TO_LOG 24
 #define MINUTES_IN_HOUR 60
+#define SECONDS_IN_MINUTE 60
+#define MS_IN_HOUR (MINUTES_IN_HOUR * SECONDS_IN_MINUTE * 1000)
+
 
 enum reportTypes { TX_LOG, RX_LOG, RX_ALL_LOG };