macio: fix overflow in lba to offset conversion for ATAPI devices

As the IDEState lba field is an int32_t, make sure we cast to int64_t before
shifting to calculate the offset. Otherwise we end up with an overflow when
trying to access sectors beyond 2GB as can occur when using DVD images.

[Maintainer edit: fixed extraneous parentheses. --js]
Signed-off-by: NMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Message-id: 1451928613-29476-1-git-send-email-mark.cave-ayland@ilande.co.uk
Signed-off-by: NJohn Snow <jsnow@redhat.com>

hw/ide/macio.c

@@ -280,7 +280,7 @@ static void pmac_ide_atapi_transfer_cb(void *opaque, int ret)
     }
 
     /* Calculate current offset */
-    offset = (int64_t)(s->lba << 11) + s->io_buffer_index;
+    offset = ((int64_t)s->lba << 11) + s->io_buffer_index;
 
     pmac_dma_read(s->blk, offset, io->len, pmac_ide_atapi_transfer_cb, io);
     return;