Commit 721449bf added support for using the
ADMA notifier bits to determine which commands to check for completion.
However there have been reports that this causes command timeouts in certain
cases. This is still being investigated. In addition, apparently the notifiers
won't work if ADMA is disabled on the other port as a result of an ATAPI device
being connected, and we don't handle this case properly.

For now, just restore the previous behavior of checking all active commands
to see if they are complete, without relying on the notifiers.
Signed-off-by: Robert Hancock <hancockr@shaw.ca>
Signed-off-by: Jeff Garzik <jeff@garzik.org>