fix a deadlock issue when poking "eject" file

"/sys/devices/LNXSYSTM:00/.../eject" is used to evaluate _EJx method
and eject a device in user space.
But system hangs when poking the "eject" file because that
the device hot-removal code invoke the driver .remove method which will
try to remove the "eject" file as a result.

Queues the hot-removal function for deferred execution in this patch.
http://bugzilla.kernel.org/show_bug.cgi?id=9772



Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>