hwui: Update configuration for 2GB/1080p devices

Change-Id: I73357a35bee22d76d3fe8a98ece91c5c9d19371d

Conflicts:
	build/phone-xxhdpi-2048-hwui-memory.mk
Add heap configuration for 1080p phones with 2048m

 * Increase heap start size to 16m to minimize GC with larger bitmaps

Change-Id: I8fbba2e5a2a2cf2d7a6898ca6bae8639d6cf5a19