Add example of delay helper function.

examples/atmega2560/src/bin/atmega2560-blink.rs

@@ -2,22 +2,31 @@
 #![no_main]
 
 use panic_halt as _;
-use atmega_hal::delay::Delay;
 use embedded_hal::delay::DelayNs;
 
 // Define core clock. This can be used in the rest of the project.
 type CoreClock = atmega_hal::clock::MHz16;
+type Delay = atmega_hal::delay::Delay<crate::CoreClock>;
+
+// Below are examples of a delay helper functions
+fn delay_ms(ms: u16) {
+    Delay::new().delay_ms(u32::from(ms))
+}
+
+#[allow(dead_code)]
+fn delay_us(us: u32) {
+    Delay::new().delay_us(us)
+}
 
 #[avr_device::entry]
 fn main() -> ! {
     let dp = atmega_hal::Peripherals::take().unwrap();
     let pins = atmega_hal::pins!(dp);
-    let mut delay = Delay::<crate::CoreClock>::new();
 
     let mut led = pins.pb7.into_output();
 
     loop {
         led.toggle();
-        delay.delay_ms(1000);
+        delay_ms(1000);
     }
 }