Base: fix the default icon for lockscreen shortcuts customisation

Use the voice assist icon instead of the dialer icon as default in the
lockscreen shortcuts customisation menu,
as this was changed in marshmallow.

https://goo.gl/photos/LGg88d7UTMiQnyoW7



Change-Id: I18c4c9bf4fd315946e2ed115294bb2bf7dc40ad3
Signed-off-by: iceandfire <arhamjamal@gmail.com>