Input: ili210x - drop get_pendown_state

The .get_pendown_state callback is set only by the platform data code,
which was just removed. Thus, get_pendown_state() always returns false,
so drop that altogether.

Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>