build(deps): bump third_party/litex-boards from ea58ef9 to c7ad9ad

Bumps [third_party/litex-boards](https://github.com/litex-hub/litex-boards) from `ea58ef9` to `c7ad9ad`.
- [Commits](litex-hub/litex-boards@ea58ef9...c7ad9ad)

---
updated-dependencies:
- dependency-name: third_party/litex-boards
  dependency-type: direct:production
...

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