Input: add driver for the Goodix touchpanel

Add a driver for the Goodix touchscreen panel found in Onda v975w tablets.
The driver is based off the Android driver gt9xx.c found in some Android
code dumps, but now bears no resemblance to the original driver.

The driver was tested on the aforementioned tablet.

Signed-off-by: Bastien Nocera <hadess@hadess.net>
Tested-by: Bastien Nocera <hadess@hadess.net>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>