Added go_defauls_common.mk for settings common to both 512 and other
Go devices. Added go_defaults_512 for 512MB RAM devices.
Bug: 67374015
Test: make, flash, look at properties
Change-Id: I160118e397a2f53d64df4a6d8e77aec3553fa401
Go devices should inherit this file to provide good default settings
for providing the best experience on Android Go devices.
Bug: 67374015
Test: make and flash
Change-Id: I55f22735c70f69309ec77e5c3055e6747546c79a