fix(README.md): outdated code example (#126)

* fix(README.md): outdated code example

* chore: add a changelog

Author: toku-sa-n

CHANGELOG.md

@@ -1,6 +1,8 @@
 # Changelog
 
 ## Unreleased - ReleaseDate
+### Fixed
+- Outdated code example in `README.md` is fixed.
 
 ## 0.8.2 - 2021-05-13
 ### Removed

README.md

@@ -18,6 +18,8 @@ This crate is `#![no_std]` compatible.
 let mut r = unsafe { xhci::Registers::new(MMIO_BASE, mapper) };
 let o = &mut r.operational;
 
-o.usbcmd.update(|u| u.set_run_stop(true));
+o.usbcmd.update(|u| {
+    u.set_run_stop();
+});
 while o.usbsts.read().hc_halted() {}
 ```