Bump yosys from ef90458 to a55e859

Bumps [yosys](https://github.com/YosysHQ/yosys) from `ef90458` to `a55e859`.
- [Release notes](https://github.com/YosysHQ/yosys/releases)
- [Commits](YosysHQ/yosys@ef90458...a55e859)

---
updated-dependencies:
- dependency-name: yosys
  dependency-type: direct:production
...

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