disk/iso: Add Support for block sizes > 512 byte to ISO partition support

For ISO we check the block size of the device if this is != the CD sector
size we assume that the device has no ISO partition.

Signed-off-by: Egbert Eich <eich@suse.com>
diff --git a/disk/part_iso.c b/disk/part_iso.c
index 49639af..cc323b0 100644
--- a/disk/part_iso.c
+++ b/disk/part_iso.c
@@ -73,6 +73,9 @@
 	iso_val_entry_t *pve = (iso_val_entry_t *)tmpbuf;
 	iso_init_def_entry_t *pide;
 
+	if (dev_desc->blksz != CD_SECTSIZE)
+		return -1;
+
 	/* the first sector (sector 0x10) must be a primary volume desc */
 	blkaddr=PVD_OFFSET;
 	if (dev_desc->block_read (dev_desc->dev, PVD_OFFSET, 1, (ulong *) tmpbuf) != 1)