recovery: Use xxhdpi resources for 560dpi devices

Create a symbolic link to res-xxhdpi for res-560dpi. 560dpi devices
(like shamu) are currently using a fallback option of xhdpi (320dpi)
resources. Now they can get closer ones (480dpi), such as larger fonts
on UI screen.

Change-Id: I427c3091d7e9892d9a7a1886be6adca14c122b06