[libata] sata_mv: Tighten up interrupt masking in mv_qc_issue()

so that it doesn't miss any protocols.  Handle future cases where a
qc is specially marked for polled issue or where a particular chip
version prefers interrupts over polling for PIO.

This mimics the polling decision logic from ata_sff_qc_issue().

Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>