[SCSI] aacraid: Check scsi_bios_ptabe return code

Received from Mark Salyzyn.

scsi_bios_ptable return value is not being checked in aac_biosparm.
Signed-off-by: NMark Haverkamp <markh@osdl.org>
Signed-off-by: NJames Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/aacraid/linit.c

@@ -325,6 +325,8 @@ static int aac_biosparm(struct scsi_device *sdev, struct block_device *bdev,
 	 *	translations ( 64/32, 128/32, 255/63 ).
 	 */
 	buf = scsi_bios_ptable(bdev);
+	if (!buf)
+		return 0;
 	if(*(__le16 *)(buf + 0x40) == cpu_to_le16(0xaa55)) {
 		struct partition *first = (struct partition * )buf;
 		struct partition *entry = first;