firewire: put old and new stack into same Kconfig submenu

firewire: put old and new stack into same Kconfig submenu

Screenshot from "make menuconfig":
...
  ?????????????????????? IEEE 1394 (FireWire) support ???????????????????????
  ?  Arrow keys navigate the menu.  <Enter> selects submenus --->.          ?
...
  ? ??????????????????????????????????????????????????????????????????????? ?
  ? ?    <M> IEEE 1394 (FireWire) support (JUJU alternative stack, experim? ?
  ? ?    <M>   Support for OHCI firewire host controllers                 ? ?
  ? ?    <M>   Support for storage devices (SBP-2 protocol driver)        ? ?
  ? ?    <M> IEEE 1394 (FireWire) support                                 ? ?
  ? ?    ---   Subsystem Options                                          ? ?
  ? ?    [ ]   Excessive debugging output                                 ? ?
...
  ?                    <Select>    < Exit >    < Help >                     ?
  ???????????????????????????????????????????????????????????????????????????

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>