submodule: bump openthread from `abcf3ba` to `71e6543` (#52)
submodule: bump openthread from `abcf3ba` to `71e6543` (#52)

Bumps [openthread](https://github.com/openthread/openthread) from `abcf3ba` to `71e6543`.
- [Commits](https://github.com/openthread/openthread/compare/abcf3ba152cd226e73e3d60217687b62613de98b...71e6543d9b207a8d06509ffeef6c276fb3f5dc2f)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>

Co-authored-by: dependabot[bot] <1c358da00a777d4e9898c1280ab801e2df165188@users.noreply.github.com>
openthread/ot-cc2538,openthread/ot-cc2538