NVMe: Fix uninitialized iod compiler warning

commit c7d36ab8fa04c213328119a9c0d66985fe204ee5 upstream.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>