firewire: cdev: use single object to dispatch event for request to IEC 61883-1 FCP region

The core function always passes the data of request to the callback of
listener in any case. Additionally, the listener can maintain the lifetime
of data by reference count. In character device, no need to duplicate the
payload of request anymore to copy it to user space.

This commit extends the lifetime of data to obsolete duplication of
payload for request in character device.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20230120090344.296451-4-o-takashi@sakamocchi.jp


Signed-off-by: Takashi Iwai <tiwai@suse.de>