media: vimc: streamer: if kthread_stop fails, ignore the error

Ignore errors returned from kthread_stop since the
vimc subdevices should still be notified that
streaming stopped so they can release the memory for
the streaming, and also kthread should be set to NULL.
kthread_stop can return -EINTR in case the thread
did not yet run. This can happen if userspace calls
streamon and streamoff right after.

Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Acked-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>