How to filter by two fields using a single exposed filter in Views?
I think you could either:


Use the Global: Combine fields filter which allows you to choose two fields (out of those already added to the display as a normal field) to filter on. The filter can be exposed, its operator changed, etc. like normal. Views warns This filter doesn't work for very special field handlers.
Use the Search: Search Terms filter. This uses search.module's data to do the query (check out the search index build mode).