HID: input: fix input sysfs path for hid devices

we used to set the parent of the input device as the parent of
the hid bus. This was introduced when we created hid as a real bus, and
to keep backward compatibility. Now, it's time to proper set the parent
so that sysfs has an idea of which input device is attached to
which hid device.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>