aic7xxx: Fix queue depth handling

We were setting the queue depth correctly, then setting it back to
two. If you hit this as a bisection point then please send me an email
as it would imply we've been hiding other bugs with this one.

Cc: <stable@vger.kernel.org>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Reviewed-by: Hannes Reinicke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>