firewire: ohci: disable MSI for VIA VT6315 again

Revert half of commit d151f98:  If isochronous I/O is attempted with
packets larget than 1 kByte, VIA VT6315 rev 01 immediately stops to generate
any interrupts if MSI are used.  Fix this by going back to legacy interrupts.
[Thread "Isochronous streaming with VT6315 OHCI",
http://marc.info/?t=139049641500003]

With smaller packets, the loss of IRQs happens too but only very rarely ---
rarely eneough that it was not yet possible for me to determine whether
QUIRK_NO_MSI is an actual fix for this rare variation of this chip bug.

I am keeping QUIRK_CYCLE_TIMER off of VT6315 rev >= 1 because this has been
verified by myself with certainty.  On the other hand, I am also keeping
QUIRK_CYCLE_TIMER on for VT6315 rev 0 because I don't know at this time
whether this revision accesses Cycle Timer non-atomically like most of the
other VIA OHCIs are known to do.

Reported-by: Rémy Bruno <remy-fw@remy.trinnov.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/ohci.c

@@ -336,10 +336,10 @@ static const struct {
 		QUIRK_CYCLE_TIMER | QUIRK_IR_WAKE},
 
 	{PCI_VENDOR_ID_VIA, PCI_DEVICE_ID_VIA_VT6315, 0,
-		QUIRK_CYCLE_TIMER | QUIRK_NO_MSI},
+		QUIRK_CYCLE_TIMER /* FIXME: necessary? */ | QUIRK_NO_MSI},
 
 	{PCI_VENDOR_ID_VIA, PCI_DEVICE_ID_VIA_VT6315, PCI_ANY_ID,
-		0},
+		QUIRK_NO_MSI},
 
 	{PCI_VENDOR_ID_VIA, PCI_ANY_ID, PCI_ANY_ID,
 		QUIRK_CYCLE_TIMER | QUIRK_NO_MSI},