Input: alps - add support for v7 devices

Such as found on the new Toshiba Portégé Z30-A and Z40-A.

Signed-off-by: Yunkang Tang <yunkang.tang@cn.alps.com>
[hdegoede@redhat.com: Remove softbutton handling, this is done in userspace]
[hdegoede@redhat.com: Report INPUT_PROP_BUTTONPAD]
[hdegoede@redhat.com: Do not report fake PRESSURE, reporting BTN_TOUCH is
 enough]
[hdegoede@redhat.com: Various cleanups / refactoring]
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>