arm64: dts: exynos: Add TM2 touchkey node

Add DT node for TM2 touchkey device.

Signed-off-by: Beomho Seo <beomho.seo@samsung.com>
Signed-off-by: Jaechul Lee <jcsing.lee@samsung.com>
Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>