build: Bump aarch64-cpu from 9.3.1 to 9.4.0

Bumps [aarch64-cpu](https://github.com/rust-embedded/aarch64-cpu) from 9.3.1 to 9.4.0.
- [Release notes](https://github.com/rust-embedded/aarch64-cpu/releases)
- [Changelog](https://github.com/rust-embedded/aarch64-cpu/blob/main/CHANGELOG.md)
- [Commits](rust-embedded/aarch64-cpu@v9.3.1...v9.4.0)

---
updated-dependencies:
- dependency-name: aarch64-cpu
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Cargo.lock

@@ -33,7 +33,7 @@ linked_list_allocator = "0.10.4"
 
 [target.'cfg(target_arch = "aarch64")'.dependencies]
 tock-registers = "0.8.1"
-aarch64-cpu = "9.3.1"
+aarch64-cpu = "9.4.0"
 fdt = "0.1.5"
 chrono = { version = "0.4", default-features = false }