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/cs5535.c b/drivers/ide/pci/cs5535.c
index dd3dc23..707d2e1 100644
--- a/drivers/ide/pci/cs5535.c
+++ b/drivers/ide/pci/cs5535.c
@@ -80,12 +80,12 @@
 
 	/* Set the PIO timings */
 	if (speed < XFER_SW_DMA_0) {
-		ide_drive_t *pair = ide_get_paired_drive(drive);
+		ide_drive_t *pair = ide_get_pair_dev(drive);
 		u8 cmd, pioa;
 
 		cmd = pioa = speed - XFER_PIO_0;
 
-		if (pair->present) {
+		if (pair) {
 			u8 piob = ide_get_best_pio_mode(pair, 255, 4);
 
 			if (piob < cmd)