drm/bridge: tc358767: disable only video stream in tc_stream_disable

Currently the code writes 0 to DP0CTL in tc_stream_disable(), which
disables the whole DP link instead of just the video stream. We always
disable the link and the stream together from tc_bridge_disable(), so
this doesn't cause any issues.

Nevertheless, fix this by only clearing VID_EN in tc_stream_disable to
stop the video stream while keeping the link enabled.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190528082747.3631-12-tomi.valkeinen@ti.com