Fix virtio-input binding while allowing hotplugging

Allow virtio-input to hotplug, while also binding the touchscreen
to the main Android UI, regardless of eventual virtioN allocation

This change requires a corresponding modification in the hypervisor
configuration to allow configuration of the vendor/product IDs for
the virtio-input device (0xfff assumed for both in this CL)

Bug: 158131006
Test: getevent -i, getevent -tld
      observe UI respond to touch events
Change-Id: I3eaa5fcc6c6562b5496fef325e22e6243b4aaa27
3 files changed