DeskClock: fix alarm ringtone layout issue

Increasing alarm volume change http://review.cyanogenmod.org/#/c/31623/
caused a layout issue with the alarm ringtone.

Before: http://i.imgur.com/yRi4eUs.png

After: http://i.imgur.com/mdXVeo8.png

Patch set 2 : Reduce row height to 48dp

Change-Id: Ib98d82e361e83a76f08550f3b74df0c6270645a8