drm/bridge: tc358767: remove check for video mode in link enable

tc_main_link_enable() checks if videomode has been set, and fails if
there's no videomode. As tc_main_link_enable() no longer depends on the
videomode, we can drop the check.

Also, while tc_stream_enable() does depend on the videomode, we can
expect that a mode has been set before drm_bridge_funcs.enable is
called, so we don't need the check there either.

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/20190528082747.3631-18-tomi.valkeinen@ti.com