sim: Directly iterate instead of using an index

From a clippy suggestion, replace an index iterator over a slice, and
directly use a mutable iterator over the slice.

Signed-off-by: David Brown <david.brown@linaro.org>

Author: d3zd3z

sim/src/image.rs

@@ -1130,15 +1130,15 @@ impl Images {
         let mut rng = rand::thread_rng();
         let mut resets = vec![0i32; count];
         let mut remaining_ops = total_ops;
-        for i in 0 .. count {
+        for reset in &mut resets {
             let reset_counter = rng.gen_range(1, remaining_ops / 2);
             let mut counter = reset_counter;
             match c::boot_go(&mut flash, &self.areadesc, Some(&mut counter), false) {
                 (0, _) | (-0x13579, _) => (),
                 (x, _) => panic!("Unknown return: {}", x),
             }
             remaining_ops -= reset_counter;
-            resets[i] = reset_counter;
+            *reset = reset_counter;
         }
 
         match c::boot_go(&mut flash, &self.areadesc, None, false) {