drm/dsi: Add Turn On/Shutdown Peripheral command helpers

The MIPI_DSI_TURN_ON_PERIPHERAL and MIPI_DSI_SHUTDOWN_PERIPHERAL packets
are required for some panels, for example the Panasonic VVX10F034N00.

Signed-off-by: Werner Johansson <werner.johansson@sonymobile.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>