arm64: dts: exynos: Add stmfts touchscreen node for TM2 and TM2E

TM2 and TM2E devices are provided with a ST-Microelectronics
Finger Tip S device with small differences:

 - screen size
 - TM2E uses the stmfts also as a touchkey for "back" and "menu"

In this commit the initial value of the interrupt line is set to
EXYNOS_PIN_PULL_UP as the interrupt is triggered when the line
goes down.

Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>