Input: auo_pixcir_ts - keep own pointer to platform_data

When supporting devicetree the platformdata may not necessarily come
from the dev but may be generated in the driver instead.

Therefore keep the pointer in the driver struct instead of using
dev.platform_data.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>