update github.com/u-root/uio

@nisse @rgdd , Consider updating this dependency, as uio introduced a braking change in the LazyOpener. This is a mess when trying to build stboot in an u-root workspace (e.g. for debugging). Aside from this, there is also an advantage in the actual change of LazyOpener as it improves logging.

Unfortunately, the update also effects the required go version.

Alternatively, consider to just remove the use of LazyOpener. This way the u-root workspace problem would be solved without any needs to update (neither uio, nor the go version)