build(deps): Bump riscv from 0.14.0 to 0.15.0

Bumps [riscv](https://github.com/rust-embedded/riscv) from 0.14.0 to 0.15.0.
- [Release notes](https://github.com/rust-embedded/riscv/releases)
- [Commits](rust-embedded/riscv@v0.14.0...riscv-v0.15.0)

---
updated-dependencies:
- dependency-name: riscv
  dependency-version: 0.15.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Cargo.lock

@@ -185,7 +185,7 @@ memory_addresses = { version = "0.2.3", default-features = false, features = [
 ] }
 
 [target.'cfg(target_arch = "riscv64")'.dependencies]
-riscv = "0.14"
+riscv = "0.15"
 sbi-rt = "0.0.3"
 semihosting = { version = "0.1", optional = true }
 tock-registers = { version = "0.10", optional = true }