Add device tree node for Mali GPU on Exynos 542x SoC family.  GPU is
disabled by default, and is enabled for each board after the regulator
is defined. Tested on Odroid XU4.
Signed-off-by: Marian Mihailescu <mihailescu2m@gmail.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>