[media] exynos-gsc: Fix unbalanced pm_runtime_enable() error

Commit a006c04e ("[media] exynos-gsc: Fixup clock management at
->remove()") changed the driver's .remove function logic to fist do
a pm_runtime_get_sync() to make sure the device is powered before
attempting to gate the gsc clock.

But the commit also removed a pm_runtime_disable() call that leads
to an unbalanced pm_runtime_enable() error if the driver is removed
and re-probed:

exynos-gsc 13e00000.video-scaler: Unbalanced pm_runtime_enable!
exynos-gsc 13e10000.video-scaler: Unbalanced pm_runtime_enable!

Fixes: a006c04e ("[media] exynos-gsc: Fixup clock management at ->remove()")

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>