clk: samsung: exynos542x: add missing parent GSCL block clocks

This patch adds clocks, which are required for preserving parent clock
configuration on GSCL power domain on/off.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>