ide: unexport DISK_EVENT_MEDIA_CHANGE for ide-gd and ide-cd

ide: unexport DISK_EVENT_MEDIA_CHANGE for ide-gd and ide-cd

check_events() implementations in both ide-gd and ide-cd are
inadequate for in-kernel event polling.  Both generate media change
events continuously when certain conditions are met causing infinite
event loop between the driver and userland event handler.

As disk event now supports suppression of unlisted events, simply
de-listing DISK_EVENT_MEDIA_CHANGE from disk->events resolves the
problem.  Internal handling around media revalidation will behave the
same while userland will fall back to userland event polling after
detecting the device doesn't support disk events.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Jens Axboe <jaxboe@fusionio.com>
Acked-by: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>