media: i2c: st_mipid02: cascade s_stream call to the source subdev

Cascade the s_stream call to the source subdev whenever the bridge
streaming is enable / disabled.

Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
Reviewed-by: Benjamin Mugnier <benjamin.mugnier@foss.st.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>