Bump yosys from 1bf908d to 6155c59

Bumps [yosys](https://github.com/YosysHQ/yosys) from `1bf908d` to `6155c59`.
- [Release notes](https://github.com/YosysHQ/yosys/releases)
- [Commits](YosysHQ/yosys@1bf908d...6155c59)

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

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