drm/exynos/fimc: fix runtime pm support

Once pm_runtime_set_active() gets called, the kernel assumes that given
device has already enabled runtime pm and will call pm_runtime_suspend()
without matching pm_runtime_resume(). In case of DRM FIMC IPP driver,
this will result in calling clk_disable() without respective call to
clk_enable(). This patch removes call to pm_runtime_set_active() to
ensure that pm_runtime_suspend/resume calls will match.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>