common/main: Add missing stopwatch in 1s event phase 2 for field log

The field log 1-second event was added to the 1-second event phase 2,
and a label was added, but the stopwatch checkpoint was overlooked to
actually measure its time.

Signed-off-by: Jonathon Hall <jonathon.hall@puri.sm>

src/board/purism/common/main.c

@@ -212,6 +212,7 @@ static void check_1s_event(void)
         labels = label_1s_checkpoints_phase2;
 
         field_log_1s_event();
+        stopwatch_checkpoint(checkpoint_times, &next_idx);
 
         // Update battery charger
         battery_charger_1s_event();