Input: gpio_mouse - kill off platform data

This is not used much: git grep  gpio_mouse_platform_data shows
that absolutely nothing in the kernel defines this platform
data.

It could be argued that the driver should be deleted. But that
is a bit harsh I think since it seems generally useful. So
this patch starts a series which repurposes it to be used with
hardware nodes from device tree or ACPI.

This first patch simply localize the platform data header and
allocates a dummy platform data.

Yes: this patch leaves the driver in a pretty useless state,
but since nothing is instantiating this driver, it doesn't
make it more useless than it already is. Later patches makes
use of the driver.

Acked-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>