[SCSI] libsas: fix NCQ mixing with non-NCQ

Some cards (like mvsas) have issue troubles if non-NCQ commands are
mixed with NCQ ones.  Fix this by using the libata default NCQ check
routine which waits until all NCQ commands are complete before issuing
a non-NCQ one.  The impact to cards (like aic94xx) which don't need
this logic should be minimal

Cc: Stable Tree <stable@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>