drm/omap: dsi: drop unused enable_te()

enable_te() is not used, so the custom API can be dropped.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201215104657.802264-20-tomi.valkeinen@ti.com