media: amphion: Remove lock in s_ctrl callback

There is no need to add a lock in s_ctrl callback, it has been
synchronized by the ctrl_handler's lock, otherwise it may led to
a deadlock if the driver calls v4l2_ctrl_s_ctrl().

Signed-off-by: Ming Qian <ming.qian@nxp.com>
Signed-off-by: Sebastian Fricke <sebastian.fricke@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>