Settings: Display information about an additional volume

Some devices have an additional internal storage volume, like emmc.
This patch adds information about this volume to the Settings screen,
"SD card & phone storage".  It also adds total size to the information
about /data storage.

Change-Id: Ia63e85f4fd373d0cff81b778dbbfcf8e90b4b8b0
Signed-off-by: Josh Stone <cuviper@gmail.com>