media: exynos4-is: add missed clk_disable_unprepare in remove

This driver forgets to disable and unprepare clock when remove.
Add a call to clk_disable_unprepare() to fix it.

Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>