drm/dsi: Support device shutdown

Hook up the MIPI DSI bus's .shutdown() function to allow drivers to
implement code that should be run when a device is shut down.

Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --cc drivers/gpu/drm/drm_mipi_dsi.c
Simple merge

diff --cc include/drm/drm_mipi_dsi.h
Simple merge