ANDROID: input: goldfish_events: no extra EV_SYN; register goldfish

If we send SYN_REPORT on every single
multitouch event, it breaks the multitouch.

The multitouch becomes janky and
having to click 2-3 times to
do stuff (plus randomly activating notification
bars when not clicking)

If we suppress these SYN_REPORTS,
multitouch will work fine, plus the events
will have a protocol that looks nice.

In addition, we need to register Goldfish Events
as a multitouch device by issuing
input_mt_init_slots, otherwise
input_handle_abs_event in drivers/input/input.c
will silently drop all ABS_MT_SLOT events,
making it so that touches with more than 1 finger
do not work properly.

Signed-off-by: "Lingfeng Yang" <lfy@google.com>
Change-Id: Ib2350f7d1732449d246f6f0d9b7b08f02cc7c2dd
(cherry picked from commit 6cf40d0a16330e1ef42bdf07d9aba6c16ee11fbc)