panic-itm: update crate config so docs aren't empty
//! panicked at 'FOO', src/main.rs:6:5
//! ```
-#![cfg(all(target_arch = "arm", target_os = "none"))]
+#![cfg(any(all(target_arch = "arm", target_os = "none"), doc))]
#![deny(missing_docs)]
#![deny(warnings)]
#![no_std]
