raw-posix: Fix /dev/cdrom magic on OS X

The raw-posix driver has code to provide a /dev/cdrom on OS X even
though it doesn't really exist. However, since commit c66a6157 the real
filename is dismissed after finding it, so opening /dev/cdrom fails.
Put the filename back into the options QDict to make this work again.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

block/raw-posix.c

@@ -1350,6 +1350,7 @@ static int hdev_open(BlockDriverState *bs, QDict *options, int flags)
                 qemu_close(fd);
             }
             filename = bsdPath;
+            qdict_put(options, "filename", qstring_from_str(filename));
         }
 
         if ( mediaIterator )