ioat: wait for self-test completion

commit 532d3b1f86f41834a25373e3ded981d68e4ce17f upstream.

As part of the ioat_dma self-test it performs a printk from a completion
callback.  Depending on the system console configuration this output can
take longer than a millisecond causing the self-test to fail.  Introduce a
completion with a generous timeout to mitigate this failure.

Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>