HID: multitouch: Apply MT_QUIRK_CONFIDENCE quirk for multi-input devices

Palm ejection stops working on some Elan and Synaptics touchpad after
commit 40d5bb87 ("HID: multitouch: enable multi-input as a quirk for
some devices").

The commit changes the mt_class from MT_CLS_WIN_8 to
MT_CLS_WIN_8_FORCE_MULTI_INPUT, so MT_QUIRK_CONFIDENCE isn't applied
anymore.

So also apply the quirk since MT_CLS_WIN_8_FORCE_MULTI_INPUT is
essentially MT_CLS_WIN_8.

Fixes: 40d5bb87 ("HID: multitouch: enable multi-input as a quirk for some devices")
Cc: stable@vger.kernel.org
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>