[SCSI] fusion: default MSI to disabled for SPI and FC controllers

There's a fault on the FC controllers that makes them not respond
correctly to MSI.  The SPI controllers are fine, but are likely to be
onboard on older motherboards which don't handle MSI correctly, so
default both these cases to disabled.  Enable by setting the module
parameter mpt_msi_enable=1.

For the SAS case, enable MSI by default, but it can be disabled by
setting the module parameter mpt_msi_enable=0.

Cc: "Prakash, Sathya" <sathya.prakash@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/message/fusion/mptbase.c

@@ -1686,9 +1686,14 @@ mpt_attach(struct pci_dev *pdev, const struct pci_device_id *id)
 		ioc->bus_type = SAS;
 	}
 
-	if (ioc->bus_type == SAS && mpt_msi_enable == -1)
-		ioc->msi_enable = 1;
-	else
+	if (mpt_msi_enable == -1) {
+		/* Enable on SAS, disable on FC and SPI */
+		if (ioc->bus_type == SAS)
+			ioc->msi_enable = 1;
+		else
+			ioc->msi_enable = 0;
+	} else
+		/* follow flag: 0 - disable; 1 - enable */
 		ioc->msi_enable = mpt_msi_enable;
 
 	if (ioc->errata_flag_1064)