sgiioc4: sgiioc4_read_status drive busy check fix

Fix the drive non-busy criterion used by sgiioc4_read_status(): neither of the
bits it expects to be set guarantees that the drive is not busy (and might be
interrupting), only the BSY bit itself being zero gurantees that.
While at it, use ATA_BUSY instead of hardcoded value everywhere...
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: jeremy@sgi.com
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/pci/sgiioc4.c

 /*
  * Copyright (c) 2003-2006 Silicon Graphics, Inc.  All Rights Reserved.
+ * Copyright (C) 2008 MontaVista Software, Inc.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of version 2 of the GNU General Public License
@@ -150,7 +151,7 @@ sgiioc4_clearirq(ide_drive_t * drive)
 		int count = 0;
 
 		stat = sgiioc4_read_status(hwif);
-		while ((stat & 0x80) && (count++ < 100)) {
+		while ((stat & ATA_BUSY) && (count++ < 100)) {
 			udelay(1);
 			stat = sgiioc4_read_status(hwif);
 		}
@@ -310,7 +311,7 @@ static u8 sgiioc4_read_status(ide_hwif_t *hwif)
 	u8 reg = (u8) readb((void __iomem *) port);
 
 	if ((port & 0xFFF) == 0x11C) {	/* Status register of IOC4 */
-		if (reg & 0x51) {	/* Not busy...check for interrupt */
+		if (!(reg & ATA_BUSY)) { /* Not busy... check for interrupt */
 			unsigned long other_ir = port - 0x110;
 			unsigned int intr_reg = (u32) readl((void __iomem *) other_ir);