drm/tilcdc: tilcdc_panel: Rename device from "panel" to "tilcdc-panel"

Rename the bundled tilcdc_panel driver from just "panel" to
"tilcdc-panel" to avoid noisy error messages from the driver trying to
probe all device nodes named "panel".

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>