drm/omap: sdi: fix bridge enable/disable

When the SDI output was converted to DRM bridge, the atomic versions of
enable and disable funcs were used. This was not intended, as that would
require implementing other atomic funcs too. This leads to:

WARNING: CPU: 0 PID: 18 at drivers/gpu/drm/drm_bridge.c:708 drm_atomic_helper_commit_modeset_enables+0x134/0x268

and display not working.

Fix this by using the legacy enable/disable funcs.

Fixes: 8bef8a6d ("drm/omap: sdi: Register a drm_bridge")
Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Tested-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: stable@vger.kernel.org # v5.7+
Link: https://patchwork.freedesktop.org/patch/msgid/20201127085241.848461-1-tomi.valkeinen@ti.com