hw/cxl/mbox: replace sanitize_running() with cxl_dev_media_disabled()

hw/cxl/mbox: replace sanitize_running() with cxl_dev_media_disabled()

The spec states that reads/writes should have no effect and a part of
commands should be ignored when the media is disabled, not when the
sanitize command is running.

Introduce cxl_dev_media_disabled() to check if the media is disabled and
replace sanitize_running() with it.

Make sure that the media has been correctly disabled during sanitation
by adding an assert to __toggle_media(). Now, enabling when already
enabled or vice versa results in an assert() failure.

Suggested-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Link: https://lore.kernel.org/r/20231222090051.3265307-4-42.hyeyoo@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20240705120643.959422-3-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>