[media] s5p-fimc: Fix bug in capture node open()

When video pipeline initialization fails, the ST_CAPT_BUSY flag
needs to be cleared before pm_runtime_put_sync is called.
Otherwise the runtime suspend routine tries to suspend device,
rather than just turning it off. Also fix potential null pointer
dereference in fimc_pipeline_shutdown().

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>