[SCSI] aacraid: bad BUG_ON fix

This was noticed by Doug Bazamic and the fix found by Mark Salyzyn at
Adaptec.

There was an error in the BUG_ON() statement that validated the
calculated fib size which can cause the driver to panic.
Signed-off-by: Mark Haverkamp <markh@osdl.org>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/aacraid/aachba.c

@@ -972,7 +972,7 @@ static int aac_read(struct scsi_cmnd * scsicmd, int cid)
 		fibsize = sizeof(struct aac_read64) + 
 			((le32_to_cpu(readcmd->sg.count) - 1) * 
 			 sizeof (struct sgentry64));
-		BUG_ON (fibsize > (sizeof(struct hw_fib) - 
+		BUG_ON (fibsize > (dev->max_fib_size - 
 					sizeof(struct aac_fibhdr)));
 		/*
 		 *	Now send the Fib to the adapter