sym53c8xx: fix "irq X: nobody cared" regression in 2.6.24

The patch described by the following excerpt from ChangeLog-2.6.24-rc1 eventually causes a "irq X: nobody cared" error after a while:

commit 99c9e0a1d6cfe1ba1169a7a81435ee85bc00e4a1

Author: Matthew Wilcox <[email protected]>
Date:   Fri Oct 5 15:55:12 2007 -0400

[SCSI] sym53c8xx: Make interrupt handler capable of returning IRQ_NONE

After this happens, the kernel disables the IRQ, causing the SCSI card to stop working until the next reboot. The problem is caused by the interrupt handler returning IRQ_NONE instead of IRQ_HANDLED after handling an interrupt-on-the-fly (INTF) condition. The following patch fixes the problem.

---

James, please queue for scsi-rc-fixes-2.6. Thanks!

@@ -2791,7 +2791,7 @@ irqreturn_t sym_interrupt(struct Scsi_Ho
 	istat = INB(np, nc_istat);
 	if (istat & INTF) {
 		OUTB(np, nc_istat, (istat & SIGP) | INTF | np->istat_sem);
-		istat = INB(np, nc_istat);		/* DUMMY READ */
+		istat |= INB(np, nc_istat);		/* DUMMY READ */
 		if (DEBUG_FLAGS & DEBUG_TINY) printf ("F ");
 		sym_wakeup_done(np);
 	}