scsi: ncr5380: Suppress unhelpful "interrupt without IRQ bit" message

If a NCR5380 host instance ends up on a shared interrupt line then
this printk will be a problem. It is already a problem on some Mac
models: when testing mac_scsi on a PowerBook 180 I found that PDMA
transfers (but not PIO transfers) cause the message to be logged.

These spurious interrupts don't appear to come from the DRQ signal from
the 5380. And they don't happen at all on the Mac LC III. A comment in
the NetBSD source code mentions this mystery. Testing seems to show
that we can safely ignore these interrupts.
Signed-off-by: NFinn Thain <fthain@telegraphics.com.au>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Tested-by: NOndrej Zary <linux@rainbow-software.org>
Tested-by: NMichael Schmitz <schmitzmic@gmail.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/NCR5380.c

@@ -995,7 +995,7 @@ static irqreturn_t __maybe_unused NCR5380_intr(int irq, void *dev_id)
 		}
 		handled = 1;
 	} else {
-		shost_printk(KERN_NOTICE, instance, "interrupt without IRQ bit\n");
+		dsprintk(NDEBUG_INTR, instance, "interrupt without IRQ bit\n");
 #ifdef SUN3_SCSI_VME
 		dregs->csr |= CSR_DMA_ENABLE;
 #endif