Input: touchscreen-gt9xx: enable the gt9xx SLOT REPORT

Input: touchscreen-gt9xx: enable the gt9xx SLOT REPORT

On the moment, the gt9xx touchscreen driver can't work on chromeos.
Since the driver report event has *not* judge correct by the chromeos.

We need report the singel point touch information for event firstly,
otherwise the chromeos will force a signel point to work.

That's seem a chromeos issue/leak.
Anyway, we can report the point including the signal information
to workaround.

Verify on rk3399evb board with chromeos.

root@localhost / # evtest
No device specified, trying to scan all of /dev/input/event*
Available devices:
/dev/input/event0:      goodix-ts
/dev/input/event1:      rk29-keypad
Select the device event number [0-1]: 0
Input driver version is 1.0.1
Input device ID: bus 0x18 vendor 0xdead product 0xbeef version 0x28bb
Input device name: "goodix-ts"
Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
  Event code 330 (BTN_TOUCH)
  Event type 3 (EV_ABS)
  Event code 0 (ABS_X)
  ...

  Event: time 1450321044.293221, type 3 (EV_ABS), code 57 (ABS_MT_TRACKING_ID), value 0
  Event: time 1450321044.293221, type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 4095
  Event: time 1450321044.293221, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 4083
  Event: time 1450321044.293221, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 8
  Event: time 1450321044.293221, type 3 (EV_ABS), code 50 (ABS_MT_WIDTH_MAJOR), value 8
  Event: time 1450321044.293221, -------------- SYN_REPORT ------------
  Event: time 1450321044.384655, type 3 (EV_ABS), code 57 (ABS_MT_TRACKING_ID), value -1
  Event: time 1450321044.384655, -------------- SYN_REPORT ------------

Change-Id: Ic41327a673632e471429ded35b68eecbbd7f3069
Signed-off-by: Caesar Wang <wxt@rock-chips.com>