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

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.

Signed-off-by: Che-Liang Chiou <clchiou@chromium.org>
BUG=chromium-os:36322
TEST=On Snow, connect Magic Mouse and perform 2-finger scroll.
     Check /var/log/Xorg.0.log and does not see error message of
     "Too many fingers! Max is 1, but I got 2"

Change-Id: Ie7fd4327935555f41577e2c8c6d6d78b52934f1a
Reviewed-on: https://gerrit.chromium.org/gerrit/41322
Commit-Queue: Che-Liang Chiou <clchiou@chromium.org>
Reviewed-by: Che-Liang Chiou <clchiou@chromium.org>
Tested-by: Che-Liang Chiou <clchiou@chromium.org>