drm/mipi-dsi: Detach devices when removing the host

In the Linux kernel, the following vulnerability has been resolved:

drm/mipi-dsi: Detach devices when removing the host

Whenever the MIPI-DSI host is unregistered, the code of

mipi_dsi_host_unregister() loops over every device currently found on that

bus and will unregister it.

However, it doesn't detach it from the bus first, which leads to all kind

of resource leaks if the host wants to perform some clean up whenever a

device is detached.