clk: samsung: exynos5250: Add DISP1 clocks

When the DISP1 power domain is powered off, there's two clocks that need
to be temporarily reparented to OSC, and back to their original parents
when the domain is powered on again.

We expose these two clocks in the DT bindings so that the DT node of the
power domain can reference them.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>