HID: magicmouse: Set multi-touch keybits for Magic Mouse

The driver emits multi-touch events for Magic Trackpad as well as Magic
Mouse, but it does not set keybits that are related to multi-touch event
for Magic Mouse; so set these keybits.

The keybits that are not set cause trouble because user programs often
probe these keybits for self-configuration and thus they cannot operate
properly if the keybits are not set.

One of such troubles is that libevdev will not be able to emit correct
touch count, causing gestures library failed to do fling stop.

Signed-off-by: Che-Liang Chiou <clchiou@chromium.org>
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>