ARM: dts: exynos: Update x and y properties for mms114 touchscreen

The mms114 binding [1] specifies that the 'x' and 'y' should be
called respectively 'touchscreen-size-x' and 'touchscreen-size-y'
in coherence with the touchscreen [2] binding.

Update the mms114 node for trats2 and trats dts according to the
binding.

[1] Documentation/devicetree/bindings/input/touchscreen/mms114.txt
[2] Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt

Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>