ide: check drive->present in ide_get_paired_drive()

* Change ide_get_paired_drive() to return NULL if peer device
  is not present and update all users accordingly.

While at it:

* ide_get_paired_drive() -> ide_get_pair_dev()

* Use ide_get_pair_dev() in cs5530.c, sc1200.c and via82cxxx.c.

There should be no functional changes caused by this patch.

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/pci/opti621.c b/drivers/ide/pci/opti621.c
index e28e672..e913da4 100644
--- a/drivers/ide/pci/opti621.c
+++ b/drivers/ide/pci/opti621.c
@@ -137,7 +137,7 @@
 static void opti621_set_pio_mode(ide_drive_t *drive, const u8 pio)
 {
 	ide_hwif_t *hwif = drive->hwif;
-	ide_drive_t *pair = ide_get_paired_drive(drive);
+	ide_drive_t *pair = ide_get_pair_dev(drive);
 	unsigned long flags;
 	u8 tim, misc, addr_pio = pio, clk;
 
@@ -153,7 +153,7 @@
 
 	drive->drive_data = XFER_PIO_0 + pio;
 
-	if (pair->present) {
+	if (pair) {
 		if (pair->drive_data && pair->drive_data < drive->drive_data)
 			addr_pio = pair->drive_data - XFER_PIO_0;
 	}