The IUs are not being fully initialised by the driver (due to the reserved
space).  Since we should be zeroing reserved fields, use kzalloc to do
it for us.

Reported-by: Luben Tuikov <ltuikov@yahoo.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>