fireworks/bebob/oxfw: remove fw_unit_get()/fw_unit_put().

They call 'cmp_connection_init()' then 'fw_iso_resources_init()' is called.
This function increment reference counter with 'fw_unit_get()'.

They also call 'cmp_connection_destroy()' then 'fw_iso_resources_destroy()' is called.
This function decrement reference counter with 'fw_unit_put()'.