media: venus: fix enc/dec destruction order

We destroy mutex-es too early as they are still taken in
v4l2_fh_exit()->v4l2_event_unsubscribe()->v4l2_ctrl_find().

We should destroy mutex-es right before kfree().  Also
do not vdec_ctrl_deinit() before v4l2_fh_exit().

Fixes: 7472c1c6 ("[media] media: venus: vdec: add video decoder files")
Suggested-by: Tomasz Figa <tfiga@google.com>
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Stanimir Varbanov <stanimir.k.varbanov@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>