Now that the receiver forwards the connect/disconnect events, we can
know when the device is available to communicate with us.

When it is ready, we can for instance retrieve its full name, which
guarantee that we always have the same name for the DJ device (the DJ
name is somewhat shorter than the HID++ name).

This mechanism is mandatory for the touchpads line, which has the
min/max information stored in the device. This information can only
be retrieved when the device is connected. So we can not populate
the input device until we are sure that the device is connected.

This patch creates a new input device for such devices. However,
this input is not bound to hid directly, so the various drivers
which wants to use it are required to process completely the
incoming reports in .raw_event().

Note that the patch in itself just adds the bits for the next
ones, and this feature is disabled by default.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Tested-by: Andrew de los Reyes <adlr@chromium.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>