sata_mv: don't issue two DMA commands concurrently

sata_mv: don't issue two DMA commands concurrently

commit 4bdee6c5103696a2729d3db2f235d202191788e4 upstream

sata_mv allowed issuing two DMA commands concurrently which the
hardware allows.  Unfortunately, libata core layer isn't ready for
this yet and spews ugly warning message and malfunctions on this.
Don't allow concurrent DMA commands for now.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Cc: Martin Michlmayr <tbm@cyrius.com>
Cc: Mark Lord <liml@rtr.ca>
Cc: Artem Bokhan <aptem@ngs.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>