[media] s5p-fimc: send valid m2m ctx to fimc_m2m_job_finish

fimc_m2m_job_finish() has to be called with the m2m context for the necessary
cleanup while resume. But currently fimc_m2m_job_finish() always passes m2m
context as NULL.
This patch preserves the context before making it null, for necessary cleanup.

Signed-off-by: Shaik Ameer Basha <shaik.ameer@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>