Apply consistent style to imports in the hardware device agent scripts

[doolio]

https://github.com/romanz/trezor-agent/blob/3c911e99a0394278104564092225d67c75e74b99/agents/trezor/trezor_agent.py#L1-L8

The style here is inconsistent with the other hardware device agent scripts. See below. If you have a preferred style I can submit a PR.

https://github.com/romanz/trezor-agent/blob/3c911e99a0394278104564092225d67c75e74b99/agents/keepkey/keepkey_agent.py#L1-L5 https://github.com/romanz/trezor-agent/blob/3c911e99a0394278104564092225d67c75e74b99/agents/jade/jade_agent.py#L1-L7 https://github.com/romanz/trezor-agent/blob/3c911e99a0394278104564092225d67c75e74b99/agents/ledger/ledger_agent.py#L1-L7 https://github.com/romanz/trezor-agent/blob/3c911e99a0394278104564092225d67c75e74b99/agents/onlykey/onlykey_agent.py#L1-L7 https://github.com/romanz/trezor-agent/blob/3c911e99a0394278104564092225d67c75e74b99/agents/fake/fake_device_agent.py#L1-L7

[romanz]

Good catch, thanks! Please submit a PR for using the style below: https://github.com/romanz/trezor-agent/blob/3c911e99a0394278104564092225d67c75e74b99/agents/trezor/trezor_agent.py#L1-L8