LED should be a `const` not a type alias

examples/blinky-blocking.rs

examples/blinky-rtc.rs

examples/blinky.rs

examples/capture1.rs

examples/capture2.rs

examples/capture4.rs

examples/concurrent.rs

examples/led.rs

examples/preemption.rs

examples/pwm-control.rs

examples/pwm1.rs

examples/pwm2.rs

examples/pwm4.rs

examples/sharing.rs

examples/wait1.rs

examples/wait2.rs

examples/wait3.rs

examples/wait4.rs

src/led.rs