Input: ALPS - fix trackstick button handling on V8 devices

Alps stick devices always have physical buttons, so we should not check
ALPS_BUTTONPAD flag to decide whether we should report them.

Fixes: 4777ac220c43 ("Input: ALPS - add touchstick support for SS5 hardware")
Signed-off-by: Masaki Ota <masaki.ota@jp.alps.com>
Acked-by: Pali Rohar <pali.rohar@gmail.com>
Tested-by: Paul Donohue <linux-kernel@PaulSD.com>
Tested-by: Nick Fletcher <nick.m.fletcher@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>