g3-common: Change LCD density to 560dpi

As quoted in device/moto/shamu/device.mk

This device is 560dpi.  However the platform doesn't
currently contain all of the bitmaps at 560dpi density so
we do this little trick to fall back to the xxhdpi version
if the 560dpi doesn't exist.

Change-Id: Ifb1153af6f3b1004046c7b0d5144c4c61c10e70f
Merge "g3-common: Change LCD density to 560dpi" into lp5.0