HID: elan: Add support for touchpad on the Toshiba Click Mini L9W

The Toshiba Click Mini L9W keyboard dock has a single i2c-hid Elan device
for both the keyboard and the touchpad. Add support for the touchpad to
the hid-elan driver, rather then relying on mouse emulation.

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