ena: Change measurement unit of time since last tx cleanup to ms
This commit:
- Sets the time since last cleanup to milliseconds.
- Fixes incorrect indentations.
Approved by: cperciva (mentor)
MFC after: 2 weeks
Sponsored by: Amazon, Inc.
(cherry picked from commit 9272e45c04c0d4fcb5d767e962783f3ab192f64e)