Follow up on commit c285f6ff6787 "firewire: remove global lock around
address handlers, convert to RCU":
- address_handler_lock no longer serializes the address handler, only
its function to serialize updates to the list of handlers remains.
Rename the lock to address_handler_list_lock.
- Callers of fw_core_remove_address_handler() must be able to sleep.
Comment on this in the API documentation.
- The counterpart fw_core_add_address_handler() is by nature something
which is used in process context. Replace spin_lock_bh() by
spin_lock() in fw_core_add_address_handler() and in
fw_core_remove_address_handler(), and document that process context
is now required for fw_core_add_address_handler().
- Extend the documentation of fw_address_callback_t.
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>