Add basic support for new suspend-block ioctls.

The new ioctls will enable the system to be more selective about
which evdev devices should hold wake-locks when their queue is
non-empty.

For now, we enable this behavior for all configured input devices,
which is more or less the status quo.  This change is mainly about
ensuring that the system still works correctly when combined with
a newer kernel that supports the suspend-block ioctls.  We can
tweak this behavior later.

Change-Id: I8ff69aa5198903f7e2998772a339313df17c0f24