drm/panel: novatek-nt36682e: don't unregister DSI device

The DSI device for the panel was registered by the DSI host, so it is an
error to unregister it from the panel driver. Drop the call to
mipi_dsi_device_unregister().

Fixes: ea4f9975 ("drm/panel: Add support for Novatek NT36672E panel driver")
Reviewed-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240404-drop-panel-unregister-v1-2-9f56953c5fb9@linaro.org