ARM: shmobile: kzm9g-reference dts: Add st1232 touchscreen node

Enable the kzm9g touchscreen controller in the board's DT file.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>