drm/bridge: tc358767: split stream enable/disable

It is nicer to have enable/disable functions instead of set(bool enable)
style function.

Split tc_main_link_stream into tc_stream_enable and tc_stream_disable.

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/20190528082747.3631-9-tomi.valkeinen@ti.com