HID: asus: Fix T100TA touchpad y dimensions

When adding the initial support I only looked at the maximum coordinates
but the Y axis is inverted, so I should have checked the minimum
coodinates which never reach 0 due to max_y being wrong, fix this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>