mcb: remove sub-device handling code

The MEN Chameleon specification states that a chameleon FPGA can include a
bridge descriptor, which then opens up a new bus behind this bridge. MCB
included subdevice handling code in the core, but no support for bus
descriptors in the parser, due to a lack of hardware access.

As this is technically dead code, but it gets executed on a device add,
I've decided to remove it.

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>