drm/exynos: gsc: minor fix for loop iteration in gsc_runtime_resume

Do not forget to call clk_disable_unprepare() on the first element of
ctx->clocks array.

Found by Linux Verification Center (linuxtesting.org).

Fixes: 8b7d3ec8

 ("drm/exynos: gsc: Convert driver to IPP v2 core API")
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>