Add TtsSpan for formatted time.

Talk back will read "Used for 3m" as "Used for 3 meters", but
it will read "Used for 3h 3m" correctly.

This cl add specific Ttsspan if the time only contains "minute"

Bug: 36379530
Test: Run SettingsRoboTests

Change-Id: I033575938cce24221980dddd9d66be4e18804541