[media] s5p-fimc: Stop media entity pipeline if fimc_pipeline_validate fails

Stops the media entity pipeline which was started earlier
if fimc_pipeline_validate fails.

[s.nawrocki: reworked to not exceed 80 characters line length]

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>