clk: samsung: exynos542x: Move G3D subsystem clocks to its sub-CMU

G3D clocks require special handling of their parent bus clock during power
domain on/off sequences. Those clocks were not initially added to the
sub-CMU handler, because that time there was no open-source driver for the
G3D (MALI Panfrost) hardware module and it was not possible to test it.

This patch fixes this issue. Parent clock for G3D hardware block is now
properly preserved during G3D power domain on/off sequence. This restores
proper MALI Panfrost performance broken by commit 8686764f


("ARM: dts: exynos: Add G3D power domain to Exynos542x").

Reported-by: Marian Mihailescu <mihailescu2m@gmail.com>
Fixes: b06a532b

 ("clk: samsung: Add Exynos5 sub-CMU clock driver")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Marian Mihailescu <mihailescu2m@gmail.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>