ioat: fix self test for multi-channel case

commit b9bdcbba010c2e49c8f837ea7a49fe006b636f41 upstream.

In the multiple device case we need to re-arm the completion and protect
against concurrent self-tests.  The printk from the test callback is
removed as it can arbitrarily delay completion of the test.

Cc: 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>